Diagnosing liposarcoma on (peri)-renal mass biopsy: A clinicopathological study of 30 cases

AIMS

Classification of renal neoplasms on small tissue biopsies is in increasing demand, and maintaining broad differential diagnostic considerations in this setting is necessary. When evaluating a renal or perirenal tumour biopsy with sarcomatoid morphology, together with sarcomatoid renal cell carcinoma and sarcomatoid urothelial carcinoma as top diagnostic considerations, it is vital to additionally consider the possibility of well-differentiated and de-differentiated liposarcoma.

METHODS AND RESULTS

This study reports a series of 30 biopsy samples from sites in or around the kidney collected from four institutions in which the correct diagnosis was either well-differentiated or de-differentiated liposarcoma. The majority (26 of 30, 87%) of lesions were accurately diagnosed on biopsy sampling, all of which incorporated testing for MDM2 by immunohistochemistry (IHC), fluorescence in-situ hybridisation (FISH) or a combination of the two as part of the diagnostic work-up. Tumour expression of MDM2 by IHC without confirmatory FISH analysis was sometimes (30%) sufficient to reach a diagnosis, but demonstration of MDM2 amplification by FISH was ascertained in the majority (57%) of biopsy samples. A diagnosis of de-differentiated liposarcoma was not definitively established until resection in four (13%) patients, as no MDM2 testing was performed on the corresponding pre-operative biopsies.

CONCLUSIONS

When a retroperitoneal tumour is not clinically suspected, histological consideration of a liposarcoma diagnosis may be overlooked. Implementation of ancillary immunohistochemical and cytogenetic testing can ultimately lead to a definitive diagnosis in this potentially misleading anatomical location.

Scattering-Based Light Sheet Microscopy Imaging of HPV-Associated Squamous Lesions of the Anal Canal: A Proof-of-Principle Study

Demand for anal cancer screening is expected to rise following the recent publication of the ANCHOR trial, which showed that treatment of HSIL significantly reduces the rate of progression to anal cancer. While screening for HPV-associated squamous lesions in the cervix is well-established and effective, this is less true for other sites in the lower anogenital tract. Current anal cancer screening and prevention rely on high-resolution anoscopy (HRA) with biopsies. This procedure has a steep learning curve for providers and may cause patient discomfort. Scattering-based light-sheet microscopy (sLSM) is a novel imaging modality with the potential to mitigate these challenges through real-time, microscopic visualization of disease-susceptible tissue. Here, we report a proof-of-principle study that establishes feasibility of dysplasia detection using an sLSM device. We imaged 110 anal biopsy specimens collected prospectively at our institution's dysplasia clinic (including 30 nondysplastic, 40 LSIL and 40 HSIL specimens) and found that these optical images are highly interpretable and accurately recapitulate histopathologic features traditionally used for the diagnosis of HPV-associated squamous dysplasia. A reader study to assess diagnostic accuracy suggests that sLSM images are noninferior to H&E for the detection of anal dysplasia (sLSM accuracy = 0.87, H&E accuracy = 0.80; p = 0.066). Given these results, we believe that sLSM technology holds great potential to enhance the efficacy of anal cancer screening by allowing accurate sampling of diagnostic tissue at the time of anoscopy. While the current imaging study was performed on ex vivo biopsy specimens, we are currently developing a handheld device for in vivo imaging that will provide immediate microscopic guidance to HRA providers.

Atypical Spindle Cell/Pleomorphic Lipomatous Tumor With Sarcomatous Transformation: Clinicopathologic and Molecular Analysis of 4 Cases

Atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) is a recently described adipocytic tumor predominantly affecting the subcutaneous soft tissues of adults. Previous studies have shown that ASPLT follows a benign clinical course with a 4% to 12% local recurrence rate and no risk of dedifferentiation. Herein, we describe the clinicopathologic and molecular findings of 4 cases of ASPLT showing unequivocal sarcomatous transformation. Three patients were male and one was female, aged 65, 70, 74, and 78 years. Two cases presented as mass-forming lesions, while 1 case was incidentally discovered. The tumors measured 30, 55, 80, and 110 mm and occurred in the chest wall (n = 2) or arm (n = 2); all were subcutaneous. Microscopically, they showed a biphasic appearance comprising a low-grade ASPLT component and a high-grade sarcomatous component. The low-grade components showed features in the spectrum of either atypical pleomorphic lipomatous tumor (n = 2) or atypical spindle cell lipomatous tumor (n = 2). The high-grade components displayed leiomyosarcoma-like (n = 2), pleomorphic liposarcoma-like (n = 1) or undifferentiated sarcoma-like (n = 1) morphology. On immunohistochemistry, tumors were negative for MDM2 and showed loss of RB1 expression. In addition, the leiomyosarcoma-like areas seen in 2 cases were positive for smooth muscle actin and H-caldesmon. Single-nucleotide polymorphism array, performed in 3 cases, showed deletions of TP53, RB1, and flanking genes in both components. In contrast, the sarcomatous components showed more complex genomic profiles with rare segmental gains and recurrent loss of PTEN (n = 3), ATM (n = 2), and CDKN2A/B (n = 2) among other genes. Whole exome sequencing identified a TP53 variant in one case and an ATRX variant in another, each occurring in both tumor components. Limited clinical follow-up showed no recurrence or metastasis after 1 to 13 months (median, 7.5 months) postsurgical excision. Altogether, our data support that ASPLT can rarely develop sarcomatous transformation and offer insights into the molecular mechanisms underlying this event.

Sarcoma microenvironment cell states and ecosystems are associated with prognosis and predict response to immunotherapy

Characterization of the diverse malignant and stromal cell states that make up soft tissue sarcomas and their correlation with patient outcomes has proven difficult using fixed clinical specimens. Here, we employed EcoTyper, a machine-learning framework, to identify the fundamental cell states and cellular ecosystems that make up sarcomas on a large scale using bulk transcriptomes with clinical annotations. We identified and validated 23 sarcoma-specific, transcriptionally defined cell states, many of which were highly prognostic of patient outcomes across independent datasets. We discovered three conserved cellular communities or ecotypes associated with underlying genomic alterations and distinct clinical outcomes. We show that one ecotype defined by tumor-associated macrophages and epithelial-like malignant cells predicts response to immune-checkpoint inhibition but not chemotherapy and validate our findings in an independent cohort. Our results may enable identification of patients with soft tissue sarcomas who could benefit from immunotherapy and help develop new therapeutic strategies.

CHRNA6 RNA In Situ Hybridization Is a Useful Tool for the Diagnosis of Extraskeletal Myxoid Chondrosarcoma

Extraskeletal myxoid chondrosarcoma (EMC) is an uncommon mesenchymal neoplasm characteristically composed of uniform-appearing round to spindle-shaped cells with eosinophilic cytoplasm and abundant myxoid extracellular matrix. Although the majority of cases harbor a pathognomonic t(9;22) translocation that fuses EWSR1 with the orphan nuclear receptor NR4A3, there are less common variants that partner NR4A3 with TAF15, TCF12, or TFG. By immunohistochemistry, EMC has features of both cartilaginous and neuroendocrine differentiation, as evidenced by inconsistent expression of S100 protein and synaptophysin or INSM1, respectively, in a subset of cases. Given the limitations of available immunohistochemical stains for the diagnosis of EMC, we analyzed genome-wide gene expression microarray data to identify candidate biomarkers based on differential expression in EMC in comparison with other mesenchymal neoplasms. This analysis pointed to CHRNA6 as the gene with the highest relative expression in EMC (96-fold; P = 8.2 × 10-26) and the only gene with >50-fold increased expression in EMC compared with other tumors. Using RNA chromogenic in situ hybridization, we observed strong and diffuse expression of CHRNA6 in 25 cases of EMC, including both EWSR1-rearranged and TAF15-rearranged variants. All examined cases of histologic mimics were negative for CHRNA6 overexpression; however, limited CHRNA6 expression, not reaching a threshold of >5 puncta or 1 aggregate of chromogen in >25% of cells, was observed in 69 of 685 mimics (10.1%), spanning an array of mesenchymal tumors. Taken together, these findings suggest that, with careful interpretation and the use of appropriate thresholds, CHRNA6 RNA chromogenic in situ hybridization is a potentially useful ancillary histologic tool for the diagnosis of EMC.

Sarcomas with EWSR1::Non-ETS Fusion (EWSR1::NFATC2 and EWSR1::PATZ1)

The wide application of increasingly advanced molecular studies in routine clinical practice has allowed a detailed, albeit still incomplete, genetic subclassification of undifferentiated round cell sarcomas. The WHO classification continues to include provisional molecular entities, whose clinicopathologic features are in the early stages of evolution. This review focuses on the clinicopathologic, molecular, and prognostic features of undifferentiated round cell sarcomas with EWSR1/FUS::NFATC2 or EWSR1::PATZ1 fusions. Classic histopathologic findings, uncommon variations, and diagnostic pitfalls are addressed, along with the utility of recently developed immunohistochemical and molecular markers.

Matrix viscoelasticity promotes liver cancer progression in the pre-cirrhotic liver

Type 2 diabetes mellitus is a major risk factor for hepatocellular carcinoma (HCC). Changes in extracellular matrix (ECM) mechanics contribute to cancer development1,2, and increased stiffness is known to promote HCC progression in cirrhotic conditions3,4. Type 2 diabetes mellitus is characterized by an accumulation of advanced glycation end-products (AGEs) in the ECM; however, how this affects HCC in non-cirrhotic conditions is unclear. Here we find that, in patients and animal models, AGEs promote changes in collagen architecture and enhance ECM viscoelasticity, with greater viscous dissipation and faster stress relaxation, but not changes in stiffness. High AGEs and viscoelasticity combined with oncogenic β-catenin signalling promote HCC induction, whereas inhibiting AGE production, reconstituting the AGE clearance receptor AGER1 or breaking AGE-mediated collagen cross-links reduces viscoelasticity and HCC growth. Matrix analysis and computational modelling demonstrate that lower interconnectivity of AGE-bundled collagen matrix, marked by shorter fibre length and greater heterogeneity, enhances viscoelasticity. Mechanistically, animal studies and 3D cell cultures show that enhanced viscoelasticity promotes HCC cell proliferation and invasion through an integrin-β1-tensin-1-YAP mechanotransductive pathway. These results reveal that AGE-mediated structural changes enhance ECM viscoelasticity, and that viscoelasticity can promote cancer progression in vivo, independent of stiffness.

GLI1-Altered Mesenchymal Tumors With ACTB or PTCH1 Fusion: A Molecular and Clinicopathologic Analysis

Mesenchymal tumors with GLI1 fusions or amplifications have recently emerged as a distinctive group of neoplasms. The terms GLI1-altered mesenchymal tumor or GLI1-altered soft tissue tumor serve as a nosological category, although the exact boundaries/criteria require further elucidation. We examined 16 tumors affecting predominantly adults (median age: 40 years), without sex predilection. Several patients had tumors of longstanding duration (>10 years). The most common primary site was soft tissue (n = 9); other sites included epidural tissue (n = 1), vertebra (n = 1), tongue (n = 1), hard palate (n = 1), and liver (n = 1). Histologically, the tumors demonstrated multinodular growth of cytologically uniform, ovoid-to-epithelioid, occasionally short spindled cells with delicate intratumoral vasculature and frequent myxoid stroma. Mitotic activity ranged from 0 to 8 mitoses/2 mm2 (mean 2). Lymphovascular invasion/protrusion of tumor cells into endothelial-lined vascular spaces was present or suspected in 6 cases. Necrosis, significant nuclear pleomorphism, or well-developed, fascicular spindle-cell growth were absent. Half demonstrated features of the newly proposed subset, "distinctive nested glomoid neoplasm." Tumors were consistently positive for CD56 (n = 5/5). A subset was stained with S100 protein (n = 7/13), SMA (n = 6/13), keratin (n = 2/9), EMA (n = 3/7), and CD99 (n = 2/6). Tumors harbored ACTB::GLI1 (n = 15) or PTCH1::GLI1 (n = 1) fusions. The assays used did not capture cases defined by GLI1 amplification. We also identified recurrent cytogenetic gains (1q, 5, 7, 8, 12, 12q13.2-ter, 21, and X). For patients with available clinical follow-up (n = 8), half were disease free. Half demonstrated distant metastases (lungs, bone, or soft tissue). Of cases without follow-up (n = 8), 2 were known recurrences, and 1 was presumed metastasis. Our results imply a more aggressive biological potential than currently reported. Given the possibility for metastasis and disease progression, even in cytologically bland, nested tumors, close clinical surveillance, akin to that for sarcoma management, may be indicated. The term GLI1-altered mesenchymal tumor with malignant potential is proposed.

Spatial transcriptomic analysis drives PET imaging of tight junction protein expression in pancreatic cancer theranostics

We apply spatial transcriptomics and proteomics to select pancreatic cancer surface receptor targets for molecular imaging and theranostics using an approach that can be applied to many cancers. Selected cancer surfaceome epithelial markers were spatially correlated and provided specific cancer localization, whereas the spatial correlation between cancer markers and immune- cell or fibroblast markers was low. While molecular imaging of cancer-associated fibroblasts and integrins has been proposed for pancreatic cancer, our data point to the tight junction protein claudin-4 as a theranostic target. Claudin-4 expression increased ∼16 fold in cancer as compared with normal pancreas, and the tight junction localization conferred low background for imaging in normal tissue. We developed a peptide-based molecular imaging agent targeted to claudin-4 with accumulation to ∼25% injected activity per cc (IA/cc) in metastases and ∼18% IA/cc in tumors. Our work motivates a new approach for data-driven selection of molecular targets.

When a dermatopathologist encounters the ultra-rare: A case series of superficial soft tissue/cutaneous myxopapillary ependymomas

Myxopapillary ependymoma (MPE) is an uncommon variant of ependymoma, almost exclusively seen in conus medullaris or filum terminale. MPE can be diagnostically challenging, especially when arising extra-axially. Here we report 5 cases of superficial soft tissue/cutaneous MPE, identified across three tertiary institutions. All patients were female and three of them (3/5, 60%) were children (median age 11 years, range 6-58 years). The tumors presented as slow-growing masses of the sacrococcygeal subcutaneous soft tissues, occasionally identified after minor trauma and clinically favored to be pilonidal sinuses. Imaging showed no neuraxis connection. Macroscopically, tumors were well-circumscribed, lobulated, and solid and microscopically they exhibited typical histopathology of MPE, at least focally. Two of the tumors (2/5, 40%) showed predominantly solid or trabecular architecture with greater cellular pleomorphism, scattered giant cells, and increased mitotic activity. All tumors (5/5, 100%) showed strong diffuse immunohistochemical expression of GFAP. One tumor clustered at the category "ependymoma, myxopapillary" by methylome analysis. Two patients (2/5, 40%) had local recurrence at 8 and 30 months after the initial surgery. No patients developed metastases during the follow-up period (median 60 months, range 6-116 months). Since a subset of extra-axial MPEs behaves more aggressively, timely and accurate diagnosis is of paramount importance.

Non-cutaneous syncytial myoepitheliomas are identical to cutaneous counterparts: a clinicopathologic study of 24 tumors occurring at diverse locations

AIMS

Cutaneous syncytial myoepithelioma (CSM) is a rare myoepithelioma variant of skin, characterized by intradermal syncytial growth of spindle cells with a distinct immunophenotype of EMA and S100 positivity and infrequent keratin expression. While CSM was first described as a cutaneous tumor, singular non-cutaneous cases have since been reported in bone. We aimed to investigate the clinicopathological features of this variant across all anatomic sites through a large multi-institutional study.

METHODS AND RESULTS

We complied a total of 24 myoepitheliomas with syncytial growth from our files. The tumors occurred in 12 male and 12 female patients (M:F = 1:1), with a median age of 31 years (range, 9-69 years). While the majority of tumors (75%, n = 18) occurred in skin, a significant subset (25%, n = 6) arose in non-cutaneous sites, including bone (n = 3), bronchus/trachea (n = 2), and interosseous membrane of tibia/fibula (n = 1). Tumor size ranged from 0.4 to 5.9 cm. Clinical follow-up (7 patients; range 14-202 months; median 56.5 months) showed a single local recurrence 8 years after incomplete skin excision but no metastases; all patients were alive at the time of last follow-up without evidence of disease. Histologically, all tumors were pink at low-power and characterized by a syncytial growth of bland ovoid, spindled, or histiocytoid cells with eosinophilic cytoplasm and prominent perivascular lymphoplasmacytic inflammation. One-third displayed adipocytic metaplasia (8/24). Rare cytologic atypia was seen but was not associated with increased mitotic activity. All tumors expressed S100, SMA, and/or EMA. Keratin expression was absent in most cases. Molecular analysis was performed in 16 cases, all showing EWSR1-rearrangments. In total, 15/15 (100%) harbored an EWSR1::PBX3 fusion, whereas 1 case EWSR1 FISH was the only molecular study performed.

CONCLUSION

Syncytial myoepithelioma is a rare but recognizable morphologic variant of myoepithelioma which may have a predilection for skin but also occurs in diverse non-cutaneous sites. Our series provides evidence supporting a reappraisal of the term "cutaneous syncytial myoepithelioma," as 25% of patients in our series presented with non-cutaneous tumors; thus, we propose the term "syncytial myoepithelioma" to aid pathologist recognition and avoidance of potentially confusing terminology when referring to non-cutaneous examples. The behavior of syncytial myoepithelioma, whether it arises in cutaneous or non-cutaneous sites, is indolent and perhaps benign with a small capacity for local recurrence.

Management Strategies and Outcomes in Primary Liver Angiosarcoma

OBJECTIVES

Primary hepatic angiosarcoma is a rare tumor of the liver that originates from endothelial and fibroblastic tissue, with poor prognosis and lack of standardized treatment. We retrospectively analyzed the clinical characteristics and treatment outcomes of 23 patients with primary liver angiosarcoma treated at an academic sarcoma center.

METHODS

We screened all patients with primary liver angiosarcoma treated at Stanford between 2000 and 2022. Data was collected from EPIC electronic medical records and included patient demographics, tumor characteristics, treatment modalities, and patient outcomes. Statistical analysis was completed using Python 3.0, while survival curves were generated using the Kaplan-Meier method and Lifelines Packages.

RESULTS

There were nearly equal numbers of males (11) and females (12) in our study, with most patients aged 70 to 79 at diagnosis. The median overall survival (OS) was 6 months (range 0.07 to 222.6 mo). The 2- and 5-year OS were both 38.6%. 71% of patients received systemic treatment with chemotherapy, while 29% received immunotherapy. Local treatment with surgery or radioembolization was performed in 14% of patients. Three patients in our study displayed particularly improved OS and received various treatments, which ranged from hepatic resection to ipilimumab/nivolumab.

CONCLUSION

Our study demonstrated that primary liver angiosarcoma has poor outcomes despite treatment. Surgical resection with negative margins is the only curative modality. However, most patients present with advanced disease and are not surgical candidates. Further research is needed to identify more effective systemic therapy options for this devastating disease.

Low-grade fibromyxoid sarcoma of the breast: genetic characterization and immunohistochemical comparison to morphologic mimics

Spindle cell lesions of the breast elicit a specific, relatively limited differential diagnosis, and accurate classification often requires careful morphologic evaluation and immunohistochemical workup. Low-grade fibromyxoid sarcoma (LGFMS) is a rare malignant fibroblastic tumor with deceptively bland spindle cell morphology. Involvement of the breast is exceedingly rare. We examined the clinicopathologic and molecular characteristics of three cases of breast/axillary LGFMS. In addition, we interrogated the immunohistochemical expression of MUC4, a commonly used marker of LGFMS, in other breast spindle cell lesions. LGFMS presented in women at 23, 33, and 59 years of age. Tumor size ranged from 0.9 to 4.7 cm. Microscopically, they were circumscribed nodular masses composed of bland spindle cells with fibromyxoid stroma. Immunohistochemically, tumors were diffusely positive for MUC4 and negative for keratin, CD34, S100 protein, and nuclear beta-catenin. Fluorescence in-situ hybridization demonstrated FUS (n = 2) or EWSR1 (n = 1) rearrangements. Next-generation sequencing identified FUS::CREB3L2 and EWSR1::CREB3L1 fusions. MUC4 immunohistochemistry performed on 162 additional breast lesions demonstrated only weak and limited expression in a subset of cases of fibromatosis (10/20, ≤30% staining), scar (5/9, ≤10%), metaplastic carcinoma (4/23, ≤5%), and phyllodes tumor (3/74, ≤10%). MUC4 was entirely negative in cases of pseudoangiomatous stromal hyperplasia (n = 9), myofibroblastoma (n = 6), periductal stromal tumor (n = 3), and cellular/juvenile fibroadenoma (n = 21). LGFMS can rarely occur in the breast and should be considered in the differential diagnosis of breast spindle cell lesions. Strong and diffuse MUC4 expression is highly specific in this histologic context. Detection of an FUS or EWSR1 rearrangement can confirm the diagnosis.

Monitoring Sarcoma Response to Immune Checkpoint Inhibition and Local Cryotherapy with Circulating Tumor DNA Analysis

PURPOSE

Immune checkpoint inhibition has led to promising responses in soft tissue sarcomas (STS), but the majority of patients do not respond and biomarkers of response will be crucial. Local ablative therapies may augment systemic responses to immunotherapy. We evaluated circulating tumor DNA (ctDNA) as a biomarker of response in patients treated on a trial combining immunotherapy with local cryotherapy for advanced STS.

PATIENTS AND METHODS

We enrolled 30 patients with unresectable or metastatic STS to a phase II clinical trial. Patients received ipilimumab and nivolumab for four doses followed by nivolumab alone with cryoablation performed between cycles 1 and 2. The primary endpoint was objective response rate (ORR) by 14 weeks. Personalized ctDNA analysis using bespoke panels was performed on blood samples collected prior to each immunotherapy cycle.

RESULTS

ctDNA was detected in at least one sample for 96% of patients. Pretreatment ctDNA allele fraction was negatively associated with treatment response, progression-free survival (PFS), and overall survival (OS). ctDNA increased in 90% of patients from pretreatment to postcryotherapy, and patients with a subsequent decrease in ctDNA or undetectable ctDNA after cryotherapy had significantly better PFS. Of the 27 evaluable patients, the ORR was 4% by RECIST and 11% by irRECIST. Median PFS and OS were 2.7 and 12.0 months, respectively. No new safety signals were observed.

CONCLUSIONS

ctDNA represents a promising biomarker for monitoring response to treatment in patients with advanced STS, warranting future prospective studies. Combining cryotherapy and immune checkpoint inhibitors did not increase the response rate of STS to immunotherapy.

Calcified Chondroid Mesenchymal Neoplasm: Exploring the Morphologic and Clinical Features of an Emergent Entity With a Series of 33 Cases

Calcified chondroid mesenchymal neoplasm is a term proposed for tumors with a spectrum of morphologic features, including cartilage/chondroid matrix formation, that frequently harbor FN1 gene fusions. We report a series of 33 cases of putative calcified chondroid mesenchymal neoplasms, mostly referred for expert consultation out of concern for malignancy. Patients included 17 males and 16 females, with a mean age of 51.3 years. Anatomic locations include the hands and fingers, feet and toes, head and neck, and temporomandibular joint; 1 patient presented with multifocal disease. Radiologic review showed soft tissue masses with variable internal calcification, which occasionally scalloped bone but in all cases appeared indolent/benign. Tumors had a mean gross size of 2.1 cm and a homogenous rubbery to fibrous/gritty tan-white cut surface. Histology demonstrated multinodular architecture with a prominent chondroid matrix and increased cellularity towards the periphery of the nodules. The tumor cells were polygonal with eccentric nuclei and bland cytologic features and showed a variable amount of increased spindled / fibroblastic forms in the perinodular septa. The majority of cases had notable grungy and/or lacy calcifications. A subset of cases demonstrated at least focal areas of increased cellularity and osteoclast-like giant cells. Herein, we confirm the distinct morphologic and clinicopathologic features associated with this entity with the largest series to date, with a focus on practical diagnostic separation from similar chondroid neoplasms. Awareness of these features is critical in avoiding pitfalls, including a malignant diagnosis of chondrosarcoma.

7-UP: Generating in silico CODEX from a small set of immunofluorescence markers

Multiplex immunofluorescence (mIF) assays multiple protein biomarkers on a single tissue section. Recently, high-plex CODEX (co-detection by indexing) systems enable simultaneous imaging of 40+ protein biomarkers, unlocking more detailed molecular phenotyping, leading to richer insights into cellular interactions and disease. However, high-plex data can be slower and more costly to collect, limiting its applications, especially in clinical settings. We propose a machine learning framework, 7-UP, that can computationally generate in silico 40-plex CODEX at single-cell resolution from a standard 7-plex mIF panel by leveraging cellular morphology. We demonstrate the usefulness of the imputed biomarkers in accurately classifying cell types and predicting patient survival outcomes. Furthermore, 7-UP's imputations generalize well across samples from different clinical sites and cancer types. 7-UP opens the possibility of in silico CODEX, making insights from high-plex mIF more widely available.

Treatment of De-Differentiated Liposarcoma in the Era of Immunotherapy

Well-differentiated/de-differentiated liposarcoma (WDLPS/DDLPS) is one of the most common histologic subtypes of soft tissue sarcoma (STS); however, treatment options remain limited. WDLPS and DDLPS both exhibit the characteristic amplification of chromosome region 12q13-15, which contains the genes CDK4 and MDM2. DDLPS exhibits higher amplification ratios of these two and carries additional genomic lesions, including the amplification of chromosome region 1p32 and chromosome region 6q23, which may explain the more aggressive biology of DDLPS. WDLPS does not respond to systemic chemotherapy and is primarily managed with local therapy, including multiple resections and debulking procedures whenever clinically feasible. In contrast, DDLPS can respond to chemotherapy drugs and drug combinations, including doxorubicin (or doxorubicin in combination with ifosfamide), gemcitabine (or gemcitabine in combination with docetaxel), trabectedin, eribulin, and pazopanib. However, the response rate is generally low, and the response duration is usually short. This review highlights the clinical trials with developmental therapeutics that have been completed or are ongoing, including CDK4/6 inhibitors, MDM2 inhibitors, and immune checkpoint inhibitors. This review will also discuss the current landscape in assessing biomarkers for identifying tumors sensitive to immune checkpoint inhibitors.

Contemporary diagnostic approach to atypical vascular lesion and angiosarcoma

Vascular neoplasms account for a substantial fraction of cutaneous mesenchymal tumors, spanning from clinically indolent benign lesions to highly aggressive malignancies. These neoplasms present a distinctive challenge in terms of their diagnostic histopathology, both because of the breadth of their morphological manifestations and because of the significant histological overlap between different entities, even benign and malignant ones. The post-radiotherapy setting is particularly problematic diagnostically, insofar as radiation exposure predisposes not only to secondary angiosarcoma, but also to atypical vascular lesion, a largely benign proliferation of cutaneous blood vessels typically affecting the breast. To address these challenges, we explore the clinical, histological, and molecular features of malignant vascular neoplasia, including primary and secondary subtypes, through the comparative lens of atypical vascular lesion. In addition to highlighting the key morphological indicators of malignancy in superficial vasoformative tumors, we offer an approach that integrates clinical characteristics and molecular genetic profiling to facilitate accurate classification. With this current knowledge as our foundation, we also look ahead in an effort to frame some of the key unanswered questions regarding superficial vascular malignancies and their natural history, clinical management, and molecular underpinnings.

The abundance and morphology of human large intestinal goblet and tuft cells during chronic schistosomiasis

Schistosomiasis affects nearly 240 million people in predominately low- and middle-income countries and ranks second in the number of cases and socio-economic burden among all parasitic diseases. Despite the enormous burden posed by schistosomes, our understanding of how schistosomiasis impacts infected human tissues remains limited. Intestinal schistosomiasis in animal models leads to goblet cell hyperplasia, likely increasing mucus production and reflecting an intestinal type 2 immune response. However, it is unknown whether these same changes occur in schistosome-infected humans. Using immunofluorescence and light microscopy, we compared the abundance and morphology of goblet cells in patients diagnosed with schistosomiasis to uninfected controls. The mucin-containing vesicles in goblet cells from schistosome-infected patients were significantly larger (hypertrophic) than uninfected individuals, although goblet cell hyperplasia was absent in chronic human schistosomiasis. In addition, we examined tuft cells in the large intestinal epithelium of control and schistosome-infected patients. Tuft cell numbers expand during helminth infection in mice, but these cells have not been characterized in human parasite infections. We found no evidence of tuft cell hyperplasia during human schistosome infection. Thus, our study provides novel insight into schistosome-associated changes to the intestinal epithelium in humans, suggesting an increase in mucus production by large intestinal goblet cells but relatively minor effects on tuft cell numbers.

Diagnostic utility of FOXO1 immunohistochemistry for rhabdomyosarcoma classification

AIMS

Rhabdomyosarcomas currently are classified into one of four subtypes (alveolar, embryonal, spindle cell/sclerosing, or pleomorphic) according to their morphological, immunohistochemical, and molecular genetic features. The alveolar subtype is characterised by a recurrent translocation involving PAX3 or PAX7 and FOXO1; identification of this translocation is important for appropriate classification and prognostication. In this study, we aimed to explore the diagnostic utility of FOXO1 immunohistochemistry for rhabdomyosarcoma classification.

METHODS/RESULTS

A monoclonal antibody targeting a FOXO1 epitope retained in the fusion oncoprotein was used to study 105 rhabdomyosarcomas. FOXO1 was positive for expression by immunohistochemistry in all 25 alveolar rhabdomyosarcomas, with 84% showing diffuse expression in greater than 90% of neoplastic cells; the remainder of alveolar rhabdomyosarcomas displayed at least moderate staining in a minimum of 60% of lesional cells. Apart from three spindle cell rhabdomyosarcomas showing heterogeneous nuclear immunoreactivity in 40-80% of tumour cells, the 80 cases of embryonal, pleomorphic, and spindle cell/sclerosing rhabdomyosarcoma were negative for FOXO1 expression (96.3% specific) when using a threshold of nuclear staining in 20% of neoplastic cells to determine positivity. Variable cytoplasmic staining was present in a fraction of all rhabdomyosarcoma subtypes. Nonneoplastic lymphocytes, endothelial cells, and Schwann cells also showed variably intense nuclear anti-FOXO1 immunoreactivity.

CONCLUSION

Taken together, our findings suggest that FOXO1 immunohistochemistry is a highly sensitive and relatively specific surrogate marker of the PAX3/7::FOXO1 fusion oncoprotein in rhabdomyosarcoma. Cytoplasmic immunoreactivity, expression in nonneoplastic tissues, and limited nuclear staining of nonalveolar rhabdomyosarcomas represent potential pitfalls in interpretation.

A spatial map of human macrophage niches reveals context-dependent macrophage functions in colon and breast cancer

Tumor-associated macrophages (TAMs) display heterogeneous phenotypes. Yet the exact tissue cues that shape macrophage functional diversity are incompletely understood. Here we discriminate, spatially resolve and reveal the function of five distinct macrophage niches within malignant and benign breast and colon tissue. We found that SPP1 TAMs reside in hypoxic and necrotic tumor regions, and a novel subset of FOLR2 tissue resident macrophages (TRMs) supports the plasma cell tissue niche. We discover that IL4I1 macrophages populate niches with high cell turnover where they phagocytose dying cells. Significantly, IL4I1 TAMs abundance correlates with anti-PD1 treatment response in breast cancer. Furthermore, NLRP3 inflammasome activation in NLRP3 TAMs correlates with neutrophil infiltration in the tumors and is associated with poor outcome in breast cancer patients. This suggests the NLRP3 inflammasome as a novel cancer immunetherapy target. Our work uncovers context-dependent roles of macrophage subsets, and suggests novel predictive markers and macrophage subset-specific therapy targets.

The Majority of Patients Who Undergo ERCP When Large Duct Obstruction Is Evident on Liver Biopsy Have Biliary Findings Amenable to Endoscopic Intervention

(1) Background: Abnormal liver function tests are commonly encountered in clinical practice, often leading to additional workup to determine the underlying etiology of these abnormal laboratory studies. As part of this evaluation, if less invasive imaging studies are performed and are without evidence of biliary obstruction, liver biopsy may be performed, and the finding of large duct obstruction on liver biopsy is commonly encountered. The utility of endoscopic retrograde cholangiopancreatography (ERCP) for evaluation and management of possible biliary obstruction in patients with large duct obstruction on liver biopsy has not been studied to date. (2) Methods: To assess the utility of ERCP in patients with large bile duct obstruction on liver biopsy, we retrospectively evaluated patients with large duct obstruction on liver biopsy from 2010-2019 at our tertiary care and transplant center. Demographic and clinical characteristics were evaluated for all patients, with sub-group analysis for patients who underwent ERCP and those who had intervenable findings at the time of ERCP. Descriptive statistics with proportions, means, and standard deviations were performed for demographics and clinical variables using absolute standardized difference. (3) Results: During the study period, 189 liver biopsies with evidence of large duct obstruction were performed. After exclusion criteria were applied, 166 unique patients were eligible for the study. Ninety-one patients with evidence of large duct obstruction on liver biopsy underwent ERCP and 75 did not. Of the 91 patients who underwent ERCP, 76 patients (84%) had an intervenable finding at ERCP. Patients who underwent ERCP were overall more likely to have had a liver transplant (65% ASD 0.63), have previously undergone cholecystectomy (80%, ASD 0.56), and be immunocompromised (80%, ASD 0.56). (4) Conclusions: ERCP is high yield when large duct obstruction is apparent on liver biopsy, with the majority of patients (84%) who undergo ERCP in this clinical context having a biliary finding necessitating therapeutic endoscopic intervention.

Adult Pancreatoblastoma: Report of 3 new Cases With Genetic Diversity and Autopsy Findings

We report the histopathological, immunohistochemical (IHC), and molecular findings in 3 patients with adult pancreatoblastoma, including 2 with autopsy features. The tumors were located in the tail and body of the pancreas, and the 2 autopsy examinations revealed liver and lung metastases. Histopathologically the neoplasms were composed of solid epithelial elements with nested or trabecular growth patterns, fibrous stroma, and squamoid clusters. Keratin 19 was positive mainly in squamoid corpuscles, and trypsin or chymotrypsin was positive in the acinar component. Neuroendocrine differentiation was observed in all tumors, and nuclear β-catenin expression in 2 tumors. Despite nuclear β-catenin expression, CTNNB1 mutation was found only in tumor 2. APC mutation was detected in tumor 1, and SMAD4 as well as MEN1 mutations in tumor 3. This last tumor also revealed chromosomal instability with many chromosomal losses and gains. The follow-up showed regional or distant metastases in all patients. Two patients died of disease after 3 and 26 months of follow-up and 1 patient is alive with no evidence of disease 6 years and 2 months after surgery. Adult pancreatoblastoma can display genetic heterogeneity, diverse histological appearance, and overlapping IHC findings. As a result, the differential diagnosis with other adult pancreatic tumors, such as acinar cell carcinoma, neuroendocrine neoplasm, solid pseudopapillary neoplasm, and mixed tumors may be challenging, especially when dealing with limited tumor tissue. The identification of squamoid corpuscles is essential for diagnosis. Although molecular findings might provide useful information, the integration of clinical, radiological, and histopathological findings is essential in pancreatoblastoma diagnosis.

Mapping transcriptional heterogeneity and metabolic networks in fatty livers at single-cell resolution

Non-alcoholic fatty liver disease is a heterogeneous disease with unclear underlying molecular mechanisms. Here, we perform single-cell RNA sequencing of hepatocytes and hepatic non-parenchymal cells to map the lipid signatures in mice with non-alcoholic fatty liver disease (NAFLD). We uncover previously unidentified clusters of hepatocytes characterized by either high or low srebp1 expression. Surprisingly, the canonical lipid synthesis driver Srebp1 is not predictive of hepatic lipid accumulation, suggestive of other drivers of lipid metabolism. By combining transcriptional data at single-cell resolution with computational network analyses, we find that NAFLD is associated with high constitutive androstane receptor (CAR) expression. Mechanistically, CAR interacts with four functional modules: cholesterol homeostasis, bile acid metabolism, fatty acid metabolism, and estrogen response. Nuclear expression of CAR positively correlates with steatohepatitis in human livers. These findings demonstrate significant cellular differences in lipid signatures and identify functional networks linked to hepatic steatosis in mice and humans.

Abstract A076: Somatic deletion of Tert inhibits clonal expansion of pancreatic acinar cell stem cells

Tert-expressing cells have been identified within the acinar cell compartment of the pancreas in mice. Lineage tracing experiments indicate that these cells can maintain the exocrine compartment during homeostasis and repopulate the tissue during regeneration. Additional expression of mutant Kras in Tert-expressing acinar cells accelerates acinar clone formation and causes transdifferentiation to pre-invasive pancreatic intraepithelial neoplasms after injury. Here, using a genetic approach, we generated mice where tamoxifen injection leads to simultaneous deletion of TERT in Tert-expressing cells and activation of a reporter allele. We performed lineage tracing experiments to investigate the role of TERT in those cells. We studied the effect of acute deletion of TERT during homeostasis, regeneration and tumorigenesis. Acute deletion of TERT significantly inhibited the clone forming capability of Tert-expressing cells during homeostasis in pancreas after one year. To explore the requirement for TERT in an injury setting, we treated mice with cerulein to induce pancreatitis. Somatic inactivagion of TERT in Tert-expressing acinar stem cells impaired clone formation in mice treated with cerulein. To understand if loss of TERT affected transformation, we deleted TERT in acinar stem cells while specifically expressing activated Kras in these cells. Acute deletion of TERT in the presence of a mutant KrasG12D allele decreased the formation of metaplastic areas and PanIN lesions post-injury. These data suggest that a functional allele of Tert is necessary for the clone forming ability of Tert-expressing cells during homeostasis and regeneration as well as acinar to ductal metaplasia and PanIN formation in tumorigenesis.

Citation Format: Patrick Neuhöfer, Stewart J. Kim, Gregory W. Charville, Steven E. Artandi. Somatic deletion of Tert inhibits clonal expansion of pancreatic acinar cell stem cells [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A076.

Interactions in CSF1-Driven Tenosynovial Giant Cell Tumors

PURPOSE

A major component of cells in tenosynovial giant cell tumor (TGCT) consists of bystander macrophages responding to CSF1 that is overproduced by a small number of neoplastic cells with a chromosomal translocation involving the CSF1 gene. An autocrine loop was postulated where the neoplastic cells would be stimulated through CSF1R expressed on their surface. Here, we use single-cell RNA sequencing (scRNA-seq) to investigate cellular interactions in TGCT.

EXPERIMENTAL DESIGN

A total of 18,788 single cells from three TGCT and two giant cell tumor of bone (GCTB) samples underwent scRNA-seq. The three TGCTs were additionally analyzed using long-read RNA sequencing. Immunofluorescence and IHC for a range of markers were used to validate and extend the scRNA-seq findings.

RESULTS

Two recurrent neoplastic cell populations were identified in TGCT that are highly similar to nonneoplastic synoviocytes. We identified GFPT2 as a marker that highlights the neoplastic cells in TCGT. We show that the neoplastic cells themselves do not express CSF1R. We identified overlapping MAB features between the giant cells in TGCT and GCTB.

CONCLUSIONS

The neoplastic cells in TGCT are highly similar to nonneoplastic synoviocytes. The lack of CSF1R on the neoplastic cells indicates they may be unaffected by current therapies. High expression of GFPT2 in the neoplastic cells is associated with activation of the YAP1/TAZ pathway. In addition, we identified expression of the platelet-derived growth factor receptor in the neoplastic cells. These findings suggest two additional pathways to target in this tumor.

Immune checkpoint upregulation in periprosthetic joint infection

Periprosthetic joint infections (PJI) induce an immunosuppressive cytokine profile through an unknown mechanism. Immune checkpoints, like programmed cell death 1 (PD-1) and its ligand (PD-L1), initiate innate immunosuppressive pathways essential for self-tolerance. Several malignancies and chronic infections co-opt these pathways to derive a survival advantage. This study evaluates PD-1/PD-L1 expression in periprosthetic tissue from patients undergoing revision hip or knee arthroplasty for a PJI versus an aseptic failure. PD-1/PD-L1 in the global tissue sample and the high-power microscopic field of maximum expression was analyzed prospectively using immunohistochemistry. Fifteen patients with a PJI (45%) and 16 patients with an aseptic failure (52%) were included. PD-1 expression was uniformly low. Maximum PD-L1 expression was upregulated in patients with a PJI (25%, interquartile range [IQR]: 5%-75%) versus an aseptic failure, (8%, IQR: 1%-48%, p = 0.039). In the PJI cohort, maximum PD-L1 expression was higher among patients who developed a recurrent PJI (68%, IQR: 53%-86% vs. 15%, IQR: 5%-70%, p = 0.039). Patients with global PD-L1 over 5% trended toward a near 22-fold increase in the odds of reinfection (odds ratio [OR]: 21.9, 95% confidence interval [CI]: 0.9-523.5, p = 0.057) and patients with maximum PD-L1 over 20% trended toward a 15-fold increase in the odds of reinfection (OR: 15.0, 95% CI: 0.6-348.9, p = 0.092). These results support immune checkpoint upregulation as a mechanism of PJI-induced local immune dysfunction. Future studies should confirm PD-L1 as a risk factor for reinfection in larger cohorts.

GRM1 Immunohistochemistry Distinguishes Chondromyxoid Fibroma From its Histologic Mimics

Chondromyxoid fibroma (CMF) is a rare benign bone neoplasm that manifests histologically as a lobular proliferation of stellate to spindle-shaped cells in a myxoid background, exhibiting morphologic overlap with other cartilaginous and myxoid tumors of bone. CMF is characterized by recurrent genetic rearrangements that place the glutamate receptor gene GRM1 under the regulatory control of a constitutively active promoter, leading to increased gene expression. Here, we explore the diagnostic utility of GRM1 immunohistochemistry as a surrogate marker for GRM1 rearrangement using a commercially available monoclonal antibody in a study of 230 tumors, including 30 CMF cases represented by 35 specimens. GRM1 was positive by immunohistochemistry in 97% of CMF specimens (34/35), exhibiting moderate to strong staining in more than 50% of neoplastic cells; staining was diffuse (>95% of cells) in 25 specimens (71%). Among the 9 CMF specimens with documented exposure to acid decalcification, 4 (44%) exhibited diffuse immunoreactivity (>95%) for GRM1, whereas all 15 CMF specimens (100%) with lack of exposure to decalcification reagents were diffusely immunoreactive ( P =0.003). High GRM1 expression at the RNA level was previously observed by quantitative reverse transcription polymerase chain reaction in 9 CMF cases that were also positive by immunohistochemistry; low GRM1 expression was observed by quantitative reverse transcription polymerase chain reaction in the single case of CMF that was negative by immunohistochemistry. GRM1 immunohistochemistry was negative (<5%) in histologic mimics of CMF, including conventional chondrosarcoma, enchondroma, chondroblastoma, clear cell chondrosarcoma, giant cell tumor of the bone, fibrous dysplasia, chondroblastic osteosarcoma, myoepithelial tumor, primary aneurysmal bone cyst, brown tumor, phosphaturic mesenchymal tumor, CMF-like osteosarcoma, and extraskeletal myxoid chondrosarcoma. These results indicate that GRM1 immunohistochemistry may have utility in distinguishing CMF from its histologic mimics.

Cutaneous Angiosarcoma of the Head and Neck-A Retrospective Analysis of 47 Patients

Simple Summary

Cutaneous angiosarcoma (CAS) is a rare sarcoma with dismal prognosis. To better characterize this disease and elucidate potential treatments that improve overall survival (OS), we conducted a retrospective study exploring clinical characteristics and treatment outcomes of 47 patients with CAS of the head and neck treated at a tertiary academic center. We found that CAS continues to have a poor prognosis with high rates of recurrence even with current treatment modalities. Surgery was highly effective in improving OS in patients with disease that could be resected with low morbidity. Chemotherapy, radiotherapy (RT), and immunotherapy did not significantly improve OS. Our findings shed light on the current landscape of clinical characteristics and treatment of CAS and could prompt further research exploring new treatment options and role of immunotherapy in the management of this difficult disease.

Abstract

Cutaneous angiosarcoma (CAS) is a rare and aggressive malignant tumor with blood vessel or lymphatic-type endothelial differentiation. It has a poor prognosis with lack of standardized treatment options. This study retrospectively evaluated the clinical characteristics and treatment outcomes of 47 patients with CAS of the head and neck treated at an academic sarcoma center. Patient data were collected from the electronic medical records. 62% of patients were male with the scalp being the most commonly affected area (64%). The majority of patients presented with localized disease (53%). Median overall survival (OS) was 3.4 years with an OS of 36% at 5 years. There was a statistically significant increase in OS for patients who underwent surgery compared to those who did not (5.4 vs. 2.8 years). In contrast, radiotherapy (RT) or chemotherapy did not significantly increase OS. 45% of patients had recurrence of disease during their treatment course with a median time to recurrence of 22.8 months. There was not a significant difference in OS for patients who underwent immunotherapy compared to those who underwent chemotherapy, although only a few patients received immunotherapy. We found that surgery was an effective treatment modality in patients with easily resectable disease, while RT, chemotherapy, and immunotherapy did not significantly improve OS.

A Subset of SMARCB1 (INI-1)-deficient vulvar neoplasms express germ cell markers

AIMS

SMARCB1 (INI-1)-deficient vulvar neoplasms comprise a group of rare tumours that include epithelioid sarcoma (ES), myoepithelial carcinoma (MEC), the recently described myoepithelioma-like tumour of the vulvar region (MELTVR), and sarcomas that are difficult to classify. It has been suggested that so-called vulvar yolk sac tumours (YST) may represent morphologic variants of SMARCB1-deficient tumours; thus, we investigated the immunoreactivity of germ cell markers in SMARCB1-deficient vulvar neoplasms.

METHODS AND RESULTS

Ten SMARCB1-deficient vulvar neoplasms were stained with germ cell tumour markers (SALL4, glypican-3, OCT3/4, and AFP) and re-reviewed for morphologic features. The tumours occurred in adult females (median age 41 years) and included ES (n = 7), MELTVR (n = 2), and MEC (n = 1). All cases showed loss of SMARCB1 expression. Four cases (40%) were focally positive for SALL4 in areas with morphology of typical-appearing ES. One of these cases also showed focal staining for OCT3/4. One ES showed a transition from typical-appearing ES to YST-like morphology, with diffuse expression of SALL4 and glypican-3, and focal expression of AFP, in these latter areas. All other tested cases were negative for AFP.

CONCLUSION

Our study reveals that SALL4, glypican-3, and OCT3/4 are positive in a subset of SMARCB1-deficient vulvar neoplasms, which may pose a diagnostic challenge and result in consideration of a germ cell tumour. We also highlight a case with transition from ES to YST-like morphology, lending further support that YSTs of the vulva are somatically derived SMARCB1-deficient neoplasms and do not represent true germ-cell neoplasia.

CDX2 expression in malignant peripheral nerve sheath tumour: a potential diagnostic pitfall associated with PRC2 inactivation

AIMS

Malignant peripheral nerve sheath tumour (MPNST) is a soft tissue sarcoma that exhibits features of Schwann cell differentiation. Heterologous, often mesenchymal-type differentiation occurs in a subset of MPNST, while glandular morphology also is encountered in rare cases. We observed in MPNST unanticipated expression of CDX2, a transcription factor that regulates intestinal epithelial differentiation, and aimed to further characterize this phenomenon.

METHODS/RESULTS

Expression of CDX2 was assessed by immunohistochemistry in a total of 32 high-grade MPNSTs lacking morphological evidence of epithelial differentiation, including twelve tumours (38%) that developed in the setting of neurofibromatosis and four (13%) in the setting of prior radiation therapy. CDX2 was expressed by 14 of 32 MPNSTs (44%), wherein immunoreactivity, varying from weak to strong, was present in 2-95% of neoplastic spindle cells (median 10%, mean 23%). Notably, CDX2 expression was limited to tumours with PRC2 inactivation (22/32; 69%), as evidenced immunohistochemically by diffuse loss of trimethylated histone H3K27. Analysing publicly available RNA-sequencing data from twelve MPNST cell lines, two of which are clonally related, we observed CDX2 expression in all six PRC2-inactivated cell lines, while CDX2 expression was negligible in six cell lines with intact PRC2, amounting to a 58-fold increase in CDX2 expression on average with PRC2 inactivation.

CONCLUSIONS

CDX2 is expressed in a subset of MPNSTs, even in the absence of morphological evidence of epithelial differentiation. CDX2 expression in MPNST is strongly associated with underlying PRC2 inactivation.

Current management and recent progress in desmoid tumors

Desmoid tumors are rare soft tissue tumors that can have aggressive infiltrative growth and relapse locally. Desmoid tumors can impact functionality and cause treatment-related morbidity and mortality. Here, the authors review current management strategies and avenues for further investigation. As part of the evolution of therapy away from primary surgical approaches to less invasive options, image-guided ablation has been accepted as less morbid and include cryoablation and high-intensity focused ultrasound. Systemic therapy options currently include hormonal agents, nonsteroidal anti-inflammatory drugs, tyrosine kinase inhibitors, and anthracycline-based regimens. Hormonal agents and nonsteroidal anti-inflammatory drugs have benign side effect profiles but generally limited efficacy. Anthracycline-based therapies are limited by the risk of secondary malignancies and cardiomyopathy. Tyrosine kinase inhibitors are well studied, and sorafenib is now one of the most utilized therapies, though limited by its side effect profile. Nirogacestat (PF-0308401) is an investigational small molecule gamma-secretase (GS) inhibitor that has demonstrated efficacy in phase 1 and II trials. A phase III trial investigating patients with desmoid tumors or aggressive fibromatosis is estimated to be completed December 2021 (NCT03785964). In addition to nirogacestat, the gamma-secretase inhibitor AL102 is being investigated for the treatment of patients with progressing desmoid tumors in the phase II/III RINGSIDE trial. Finally, the beta-catenin inhibitor Tegavivint (BC2059) is being investigated in a phase 1 open-label trial in patients with a proven primary or recurrent desmoid tumor that is unresectable and symptomatic or progressive.

Immune imprinting, breadth of variant recognition, and germinal center response in human SARS-CoV-2 infection and vaccination

During the SARS-CoV-2 pandemic, novel and traditional vaccine strategies have been deployed globally. We investigated whether antibodies stimulated by mRNA vaccination (BNT162b2), including third-dose boosting, differ from those generated by infection or adenoviral (ChAdOx1-S and Gam-COVID-Vac) or inactivated viral (BBIBP-CorV) vaccines. We analyzed human lymph nodes after infection or mRNA vaccination for correlates of serological differences. Antibody breadth against viral variants is lower after infection compared with all vaccines evaluated but improves over several months. Viral variant infection elicits variant-specific antibodies, but prior mRNA vaccination imprints serological responses toward Wuhan-Hu-1 rather than variant antigens. In contrast to disrupted germinal centers (GCs) in lymph nodes during infection, mRNA vaccination stimulates robust GCs containing vaccine mRNA and spike antigen up to 8 weeks postvaccination in some cases. SARS-CoV-2 antibody specificity, breadth, and maturation are affected by imprinting from exposure history and distinct histological and antigenic contexts in infection compared with vaccination.

Well-differentiated lipomatous neoplasms with p53 alterations: a clinicopathological and molecular study of eight cases with features of atypical pleomorphic lipomatous tumour

AIMS

Well-differentiated lipomatous neoplasms encompass a broad spectrum of benign and malignant tumours, many of which are characterised by recurrent genetic abnormalities. Although a key regulator of p53 signalling, MDM2, is characteristically amplified in well-differentiated liposarcoma, recurrent abnormalities of p53 itself have not been reported in well-differentiated adipocytic neoplasms. Here, we present a series of well-differentiated lipomatous tumours characterised by p53 alterations and histological features in keeping with atypical pleomorphic lipomatous tumour (APLT).

METHODS AND RESULTS

We reviewed the morphological, immunohistochemical and molecular genetic features of eight lipomatous tumours with p53 alterations. Four tumours arose in the thigh, and one case each arose in the shoulder, calf, upper back, and subclavicular regions; six tumours were deep/subfascial and two were subcutaneous. Relevant clinical history included two patients with Li-Fraumeni syndrome. Morphologically, all cases showed well-differentiated adipocytes with prominent nuclear pleomorphism, limited mitotic activity, and no tumour cell necrosis. All cases were negative for MDM2 overexpression and amplification as determined with immunohistochemistry and fluorescence in-situ hybridisation, respectively. Immunohistochemically, p16 was diffusely overexpressed in all cases; seven tumours (88%) showed abnormal loss of Rb and p53. TP53 mutation or deletion was identified in four of six tumours evaluated with exon-targeted hybrid capture-based massively parallel sequencing; RB1 mutation or deletion was present in five of six cases.

CONCLUSIONS

We present a series of eight well-differentiated lipomatous neoplasms characterised by p53 alterations in addition to Rb loss and histological features of APLT. These findings suggest that impaired p53 signalling may contribute to the pathogenesis of APLT in a subset of cases.

Diagnosis of soft tissue tumors using immunohistochemistry as a surrogate for recurrent fusion oncoproteins

Soft tissue neoplasms encompass a broad spectrum of clinicopathologic manifestations. In a subset of soft tissue tumors, spanning a wide range of clinical behavior from indolent to highly aggressive, recurrent genetic translocations yield oncogenic fusion proteins that drive neoplastic growth. Beyond functioning as primary mechanisms of tumorigenesis, recurrent translocations represent key diagnostic features insofar as the presence of a particular oncogenic gene fusion generally points to specific tumor entities. In addition to more direct methods for identifying recurrent translocations, such as conventional cytogenetics or fluorescence in situ hybridization, immunohistochemistry for a component of the fusion oncoprotein increasingly is being used as a surrogate marker, exploiting the tendency of these fusion components to be distinctively overexpressed by translocation-bearing tumor cells. Diagnostic immunohistochemistry can also be used to identify the characteristic gene expression changes that occur downstream of oncogenic fusions. Here, we review the use of immunohistochemistry to detect surrogate markers of recurrent translocations in soft tissue tumors, focusing on the practical applications and limitations of this diagnostic approach.

A Retrospective Comparative Analysis of Outcomes and Prognostic Factors in Adult and Pediatric Patients with Osteosarcoma

Osteosarcoma is the most common primary bone malignancy in both children and adults. Despite introduction of intensive multimodal treatment with chemotherapy and surgery, outcomes are still poor, especially for patients with metastatic disease and adults. Hence, there is an ongoing need for better prognostic markers and outcome data to inform management decisions in both the adult and pediatric setting. Here, we retrospectively analyzed 112 patients with bone osteosarcoma treated at two large adult and pediatric tertiary academic centers between 1989 and 2019. Patients were divided into an adult (≥18 years) and pediatric (<18 years) cohort for comparison. Our aim was to evaluate predictors of outcomes in pediatric and adult patients, with a specific focus on the role of methotrexate when added to a combination of doxorubicin-cisplatin; the prognostic value of tumor necrosis after neoadjuvant chemotherapy; and outlining any differences in outcomes between adults and pediatric patients that could inform clinical management. Adult patients treated with methotrexate-doxorubicin-cisplatin and those treated with doxorubicin-cisplatin had similar 5-year PFS (26%, 95%CI: 45.5%–10% vs. 50%, 95%CI: 69.6%–26.2%, p = 0.1) and 5-year OS (63%, 95%CI: 82%–34%, vs. 78%, 95%CI: 90.6%–52.6%, p = 0.5). In the adult cohort, there was no difference between patients with ≥90% necrosis and <90% necrosis in either 5-year PFS (42%, 95%CI: 71.1%–11.3% vs. 38%, 95%CI: 57.7%–18.2%, p = 0.4) or 5-year OS (85%, 95%CI: 97.8%–33.4% vs. 56%, 95%CI: 76.8%–27.6%, p = 0.4). In the pediatric cohort, compared to patients with <90% necrosis, those with ≥90% necrosis had significantly better 5-year PFS (30%, 95%CI: 49.3%–14.1% vs. 55%, 95%CI: 73.9%–38.5%, p = 0.003) and 5-year OS (64%, 95%CI: 80.8%–41.1% vs. 78%, 95%CI: 92%–60.9%, p = 0.04). Adult and pediatric patients had similar 5-year OS (69%, 95%CI: 83.2%–49.8% vs. 73%, 95%CI: 83.2%–59.3%, p = 0.8) and 5-year PFS (37%, 95%CI: 52.4%–22.9% vs. 43%, 95%CI: 56.2%–30.4% p = 0.3) even though the proportion of patients with ≥90% necrosis after neoadjuvant chemotherapy was higher for children compared to adults (60.3% vs. 30%, OR: 3.54, 95%CI: 1.38–8.46, p = 0.006). In conclusion, in adult patients, the addition of methotrexate to doxorubicin and cisplatin did not correlate with a significant survival benefit, questioning the therapeutic value of methotrexate overall. Our study confirms the prognostic utility of percent tumor necrosis after neoadjuvant chemotherapy in pediatric patients but not in adult patients. Lastly, this is one of the few reported studies where patients with osteosarcoma younger and older than 18 years had similar PFS and OS.

Acinar cell clonal expansion in pancreas homeostasis and carcinogenesis

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer deaths worldwide¹. Studies in human tissues and in mouse models have suggested that for many cancers, stem cells sustain early mutations driving tumour development^2,3. For the pancreas, however, mechanisms underlying cellular renewal and initiation of PDAC remain unresolved. Here, using lineage tracing from the endogenous telomerase reverse transcriptase (Tert) locus, we identify a rare TERT-positive subpopulation of pancreatic acinar cells dispersed throughout the exocrine compartment. During homeostasis, these TERT^high acinar cells renew the pancreas by forming expanding clones of acinar cells, whereas randomly marked acinar cells do not form these clones. Specific expression of mutant Kras in TERT^high acinar cells accelerates acinar clone formation and causes transdifferentiation to ductal pre-invasive pancreatic intraepithelial neoplasms by upregulating Ras-MAPK signalling and activating the downstream kinase ERK (phospho-ERK). In resected human pancreatic neoplasms, we find that foci of phospho-ERK-positive acinar cells are common and frequently contain activating KRAS mutations, suggesting that these acinar regions represent an early cancer precursor lesion. These data support a model in which rare TERT^high acinar cells may sustain KRAS mutations, driving acinar cell expansion and creating a field of aberrant cells initiating pancreatic tumorigenesis.

Quantitative image features from radiomic biopsy differentiate oncocytoma from chromophobe renal cell carcinoma

Purpose: To differentiate oncocytoma and chromophobe renal cell carcinoma (RCC) using radiomics features computed from spherical samples of image regions of interest, "radiomic biopsies" (RBs). Approach: In a retrospective cohort study of 102 CT cases [68 males (67%), 34 females (33%); mean age ± SD, 63 ± 12    years ], we pathology-confirmed 42 oncocytomas (41%) and 60 chromophobes (59%). A board-certified radiologist performed two RB rounds. From each RB round, we computed radiomics features and compared the performance of a random forest and AdaBoost binary classifier trained from the features. To control for overfitting, we performed 10 rounds of 70% to 30% train-test splits with feature-selection, cross-validation, and hyperparameter-optimization on each split. We evaluated the performance with test ROC AUC. We tested models on data from the other RB round and compared with the same round testing with the DeLong test. We clustered important features for each round and measured a bootstrapped adjusted Rand index agreement. Results: Our best classifiers achieved an average AUC of 0.71 ± 0.024 . We found no evidence of an effect for RB round ( p = 1 ). We also found no evidence for a decrease in model performance when tested on the other RB round ( p = 0.85 ). Feature clustering produced seven clusters in each RB round with high agreement ( Rand index = 0.981 ± 0.002 , p < 0.00001 ). Conclusions: A consistent radiomic signature can be derived from RBs and could help distinguish oncocytoma and chromophobe RCC.

Nuclear expression of DDIT3 distinguishes high-grade myxoid liposarcoma from other round cell sarcomas

Myxoid liposarcoma (MLPS) is a malignant adipocytic neoplasm with predilection for the extremities. MLPS is genetically defined by a t(12;16) translocation leading to FUS-DDIT3 (95%) or more rarely t(12;22) leading to EWSR1-DDIT3. Low-grade MLPS is characterized by bland spindle cells within a myxoid matrix containing delicate "chicken-wire" vasculature, whereas high-grade ("round cell") MLPS may be indistinguishable from other round cell sarcomas. In many cases, cytogenetic or molecular genetic techniques are applied to confirm the diagnosis. A recent study documented the utility of DDIT3 immunohistochemistry (IHC) in the differential diagnosis of adipocytic and myxoid soft tissue tumors. The purpose of this study was to evaluate DDIT3 IHC as a surrogate for molecular testing in high-grade MLPS. IHC was performed using a mouse monoclonal antibody directed against the N-terminus of DDIT3 on whole tissue sections from 50 high-grade MLPS cases and 319 histologic mimics used as controls (170 on whole tissue sections and 149 on a tissue microarray). Histologic mimics included Ewing sarcoma, CIC-rearranged sarcoma, sarcomas with BCOR genetic alterations, poorly differentiated synovial sarcoma, alveolar and embryonal rhabdomyosarcomas, mesenchymal chondrosarcoma, desmoplastic small round cell tumor, and neuroblastoma. Nuclear staining in >5% of cells was considered positive. By IHC, 48 (96%) high-grade MLPS showed strong diffuse nuclear staining for DDIT3. Of the controls, 2% of cases were positive, with no more than 25% nuclear staining. An additional 19% of control cases displayed less than 5% nuclear staining. Overall, DDIT3 IHC showed 96% sensitivity and 98% specificity for high-grade MLPS; strong, diffuse staining is also 96% sensitive but is 100% specific. IHC using an antibody directed against the N-terminus of DDIT3 is highly sensitive and specific for high-grade MLPS among histologic mimics and could replace molecular genetic testing in many cases, although limited labeling may be seen in a range of other tumor types.

Hereditary inflammatory fibroid polyps caused by germline pathogenic variants in PDGFRA: Refining PDGFRA-mutation syndrome

A 35-year-old Filipino woman presented with epigastric pain and was found to have two large jejunal and ileal inflammatory fibroid polyps (IFPs) and dozens of subcentimeter small bowel submucosal nodules. Targeted exon sequencing of PDGFRA on the resected jejunum IFP identified a variant c.1664A>G that was subsequently confirmed in the germline. Family history was striking for three relatives with confirmed IFPs, including one with small bowel intussusception on five occasions. All relatives with IFPs were confirmed to have the same PDGFRA germline likely pathogenic variant, all were female, and all had IFPs by age 50 years that necessitated surgery. Two obligate carriers were reported to have had a similar phenotype while at least one obligate male carrier had no reported history of IFPs. This is the sixth reported family with a germline PDGFRA pathogenic variant and history of IFPs or gastrointestinal stromal tumor (GIST). This is the second report of the c.1664A>G likely pathogenic variant in a family that is unrelated to, and of different ethnic origin than, the first family. This second family exhibited a striking history of multiple IFPs without any reported GISTs, suggesting a possible genotype/phenotype association for this variant, and a possible female gender penetrance bias.

MUC4 is expressed in alveolar rhabdomyosarcoma

AIMS

Mucin 4 (MUC4) is a transmembrane glycoprotein normally expressed by several human epithelial surfaces, including those of the colon, vagina, and respiratory tract. Although MUC4 overexpression is seen in various carcinomas, its expression among mesenchymal neoplasms is fairly specific to low-grade fibromyxoid sarcoma and sclerosing epithelioid fibrosarcoma. Having observed unanticipated anti-MUC4 immunoreactivity in rhabdomyosarcoma, we aimed to further characterise its expression.

METHODS AND RESULTS

Expression of MUC4 was assessed by immunohistochemistry in a total of 97 rhabdomyosarcomas using formalin-fixed paraffin-embedded tissue sections. MUC4 was expressed by 21 of 26 PAX3/7-FOXO1 fusion-positive cases, wherein immunoreactivity, varying from weak to strong, was present in 20-100% of neoplastic cells. With the exception of one sclerosing rhabdomyosarcoma showing immunoreactivity in 20% of cells, MUC4 was not expressed by embryonal (n = 28), sclerosing (n = 20), or pleomorphic (n = 23) rhabdomyosarcomas. Analysing published gene expression microarray data from a separate cohort of 33 fusion-positive and 25 fusion-negative rhabdomyosarcomas, we found on average a 11.4-fold increased expression in fusion-positive tumours (P = 0.0004).

CONCLUSIONS

MUC4 is expressed to a variable extent in the majority of PAX3/7-FOXO1 fusion-positive (alveolar) rhabdomyosarcomas, while expression in other rhabdomyosarcoma subtypes is rare.

AGER1 downregulation associates with fibrosis in nonalcoholic steatohepatitis and type 2 diabetes

Type 2 diabetes is clinically associated with progressive necroinflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Advanced glycation end-products (AGEs) accumulate during prolonged hyperglycemia, but the mechanistic pathways that lead to accelerated liver fibrosis have not been well defined. In this study, we show that the AGEs clearance receptor AGER1 was downregulated in patients with NASH and diabetes and in our NASH models, whereas the proinflammatory receptor RAGE was induced. These findings were associated with necroinflammatory, fibrogenic, and pro-oxidant activity via the NADPH oxidase 4. Inhibition of AGEs or RAGE deletion in hepatocytes in vivo reversed these effects. We demonstrate that dysregulation of NRF2 by neddylation of cullin 3 was linked to AGER1 downregulation and that induction of NRF2 using an adeno-associated virus-mediated approach in hepatocytes in vivo reversed AGER1 downregulation, lowered the level of AGEs, and improved proinflammatory and fibrogenic responses in mice on a high AGEs diet. In patients with NASH and diabetes or insulin resistance, low AGER1 levels were associated with hepatocyte ballooning degeneration and ductular reaction. Collectively, prolonged exposure to AGEs in the liver promotes an AGER1/RAGE imbalance and consequent redox, inflammatory, and fibrogenic activity in NASH.

DDIT3 Immunohistochemistry Is a Useful Tool for the Diagnosis of Myxoid Liposarcoma

Myxoid liposarcoma is a malignant adipogenic neoplasm characterized by prominent arborizing capillaries, occasional lipoblasts, and primitive-appearing spindle cells in a myxoid background. A recurrent translocation in myxoid liposarcoma results in an oncoprotein consisting of full-length DDIT3 (CHOP) fused to an N-terminal segment of either FUS (TLS) or, less often, EWSR1. Here, we explore the diagnostic significance of DDIT3 expression in myxoid liposarcoma using a mouse monoclonal antibody recognizing an epitope in the N-terminal region. Studying a total of 300 tumors, we find diffuse, moderate-to-strong nuclear-localized anti-DDIT3 immunoreactivity in all 46 cases of myxoid liposarcoma representing 36 unique tumors, including 6 cases with high-grade (round cell) morphology. DDIT3 immunohistochemistry also highlighted a distinctive vasculocentric growth pattern in 7 myxoid liposarcomas treated with neoadjuvant radiation. In contrast, the vast majority of other examined lipomatous and myxoid neoplasms exhibited no DDIT3 expression; limited, weak immunoreactivity in <10% of cells was infrequently observed in dedifferentiated liposarcoma (6/39, 15%), solitary fibrous tumor (3/12, 25%), pleomorphic liposarcoma (1/15, 7%), and high-grade myxofibrosarcoma (2/17, 12%). Although this minimal DDIT3 expression did not correlate with DDIT3 amplification or myxoid liposarcoma-like morphology in dedifferentiated liposarcoma, there was evidence among sarcomas (excluding myxoid liposarcoma) of a relationship between expression and exposure to neoadjuvant radiation or cytotoxic chemotherapy. The constellation of findings indicates that DDIT3 immunohistochemistry may have utility in the evaluation of myxoid and lipomatous neoplasms to support the diagnosis of myxoid liposarcoma.

Sinonasal FUS-ERG-Rearranged Ewing's Sarcoma Mimicking Glomangiopericytoma

Ewing's sarcoma is a rare and aggressive tumor that typically arises in the long bones of the extremities. It belongs in the family of small round blue cell tumors and is characterized immunohistochemically by diffuse CD99 expression and molecularly by one of several oncogenic translocations, most commonly t(11;22)(q24;q12) between the EWSR1 gene and the FLI1 gene. Here we present a rare case of Ewing's sarcoma in the sinonasal tract with FUS-ERG gene arrangement that was regarded for almost a decade as a sinonasal-type hemangiopericytoma (glomangiopericytoma). This case illustrates the surprisingly prolonged natural history of Ewing's sarcoma that did not receive therapy for many years and the importance of considering alternative genetic translocations. Our experience suggests that the presence of diffuse CD99 membranous staining pattern in a small blue round cell tumor with morphology typical for Ewing's sarcoma but FISH negative for EWSR1 rearrangement should prompt consideration of FUS-ERG fusion.

Clinicopathologic characterization of malignant chondroblastoma: a neoplasm with locally aggressive behavior and metastatic potential that closely mimics chondroblastoma-like osteosarcoma

Chondroblastoma is currently classified as a benign neoplasm; however, chondroblastoma and chondroblastoma-like osteosarcoma have morphologic overlap, raising the possibility that some tumors diagnosed as chondroblastoma-like osteosarcoma might actually represent malignant chondroblastoma. The H3F3B K36M point mutation, which has not been reported in osteosarcoma, is identified in 95% of chondroblastomas and is reliably detectable by immunohistochemistry (IHC). We reviewed 11 tumors diagnosed as atypical chondroblastoma, malignant chondroblastoma, or chondroblastoma-like osteosarcoma (median follow-up: 8.8 years; range: 4 months-26.4 years). Seven chondroblastomas with cytologic atypia and permeative growth were designated "malignant chondroblastoma"; six were H3K36M-positive by IHC. Relative to conventional chondroblastoma, malignant chondroblastoma occurred in older individuals (median: 52 years; range: 29-57 years) and arose at unusual sites. Three of four tumors with long-term follow-up recurred, and one patient died of widespread metastases. One was found to have chromosomal copy number alter4ations and a SETD2 mutation in addition to H3F3B K36M. The four remaining tumors were classified as chondroblastoma-like osteosarcoma. Chondroblastoma-like osteosarcoma occurred in younger patients (median: 21 years; range: 19-40 years) than malignant chondroblastoma. In contrast to malignant chondroblastoma, all had regions of malignant cells forming bone. Two of three patients with long-term follow-up developed recurrences, and two died of disease, one with widespread metastases. No mutations in H3F3A/H3F3B were detected by Sanger sequencing. While malignant chondroblastoma and chondroblastoma-like osteosarcoma show significant morphologic overlap, they have distinct clinical presentations and genetic findings. When considering this challenging differential diagnosis, IHC using histone H3 mutation-specific antibodies is a critical diagnostic adjunct.

Nonphagocytic Activation of NOX2 Is Implicated in Progressive Nonalcoholic Steatohepatitis During Aging

BACKGROUND AND AIMS

Older patients with obesity/type II diabetes mellitus frequently present with advanced NASH. Whether this is due to specific molecular pathways that accelerate fibrosis during aging is unknown. Activation of the Src homology 2 domain-containing collagen-related (Shc) proteins and redox stress have been recognized in aging; however, their link to NASH has not been explored.

APPROACH AND RESULTS

Shc expression increased in livers of older patients with NASH, as assessed by real time quantitative PCR (RT-qPCR) or western blots. Fibrosis, Shc expression, markers of senescence, and nicotinamide adenine dinucleotide phosphate, reduced form oxidases (NOXs) were studied in young/old mice on fast food diet (FFD). To inhibit Shc in old mice, lentiviral (LV)-short hairpin Shc versus control-LV were used during FFD. For hepatocyte-specific effects, floxed (fl/fl) Shc mice on FFD were injected with adeno-associated virus 8-thyroxine-binding globulin-Cre-recombinase versus control. Fibrosis was accelerated in older mice on FFD, and Shc inhibition by LV in older mice or hepatocyte-specific deletion resulted in significantly improved inflammation, reduction in senescence markers in older mice, lipid peroxidation, and fibrosis. To study NOX2 activation, the interaction of p47^phox (NOX2 regulatory subunit) and p52Shc was evaluated by proximity ligation and coimmunoprecipitations. Palmitate-induced p52Shc binding to p47^phox , activating the NOX2 complex, more so at an older age. Kinetics of binding were assessed in Src homology 2 domain (SH2) or phosphotyrosine-binding (PTB) domain deletion mutants by biolayer interferometry, revealing the role of SH2 and the PTB domains. Lastly, an in silico model of p52Shc/p47^phox interaction using RosettaDock was generated.

CONCLUSIONS

Accelerated fibrosis in the aged is modulated by p52Shc/NOX2. We show a pathway for direct activation of the phagocytic NOX2 in hepatocytes by p52Shc binding and activating the p47^phox subunit that results in redox stress and accelerated fibrosis in the aged.

Tenosynovial giant cell tumor of the suboccipital region - A rare, benign neoplasm in this location

Tenosynovial giant cell tumors (TGCTs) are benign neoplasms that arise from the synovium of tendon sheaths, bursae, and joints. We report a rare presentation of TGCT involving the suboccipital spine.