Myxoid cutaneous tumors: a review

A Rare Case of Myxoid Solitary Fibrous Tumor of the Upper Lip: The Key Role of STAT6 in Diagnosis

A solitary fibrous tumor (SFT) is an uncommon spindle cell mesenchymal neoplasm that most commonly arises in the pleura. SFTs have been shown to arise in various internal organs but are not typically discovered cutaneously. The diagnosis of SFT requires an integrated approach since SFT can mimic a variety of benign and malignant tumors, both clinically and histologically. To further complicate the histological diagnosis, there are different morphological variants of SFT. Therefore, immunohistochemical markers such as signal transducer and activator of transcription 6 (STAT6) can be utilized for SFT diagnosis due to their high specificity and sensitivity, as nuclear expression of STAT6 is a distinguishing feature of SFT and helps differentiate it from histological mimickers. A correct diagnosis is imperative for proper treatment and management. In this report, we present a 74-year-old healthy man with a growing painless mass on his upper lip for several years. Biopsy results confirmed the diagnosis of SFT with myxoid variation, and the patient underwent a successful excision of the lesion. Our case emphasizes the importance of a multidisciplinary approach and the utilization of immunohistochemical staining when diagnosing superficial tumors.

Mesenchymal Tumors of the Skin: A Review

Mesenchymal tumors of the skin are rare and clinically heterogeneous, and can represent diagnostic challenge for pathologists. Most of these lesions have overlapping clinical and histological features, thus the understanding of architectural patterns, cytoplasmic and stromal features can facilitate proper diagnosis. Anatomic site may be an important factor in the differential diagnosis, as are patient's age and sex. Ancillary tests are often required and can be useful to rule out other entities. Molecular diagnostics is playing an increasingly important role in the diagnosis of soft tissue neoplasms. Here, we review clinical, histological, and molecular features of some of the most common of these uncommon entities including benign and malignant lesions.

Pan-cancer Genomic Analysis of AXL Mutations Reveals a Novel, Recurrent, Functionally Activating AXL W451C Alteration Specific to Myxofibrosarcoma

Myxofibrosarcoma (MFS) is a common soft tissue sarcoma of the elderly that typically shows low tumor mutational burden, with mutations in TP53 and in genes associated with cell cycle checkpoints ( RB1 , CDKN2A ). Unfortunately, no alterations or markers specific to MFS have been identified and, as a consequence, there are no effective targeted therapies. The receptor tyrosine kinase AXL, which drives cellular proliferation, is targetable by new antibody-based therapeutics. Expression of AXL messenger RNA is elevated in a variety of sarcoma types, with the highest levels reported in MFS, but the pathogenic significance of this finding remains unknown. To assess a role for AXL abnormalities in MFS, we undertook a search for AXL genomic alterations in a comprehensive genomic profiling database of 463,546 unique tumors (including 19,879 sarcomas, of which 315 were MFS) interrogated by targeted next-generation DNA and/or RNA sequencing. Notably, the only genomic alterations recurrent in a specific sarcoma subtype were AXL W451C (n = 8) and AXL W450C (n = 2) mutations. The tumors involved predominantly older adults (age: 44 to 81 [median: 72] y) and histologically showed epithelioid and spindle-shaped cells in a variably myxoid stroma, with 6 cases diagnosed as MFS, 3 as undifferentiated pleomorphic sarcoma (UPS), and 1 as low-grade sarcoma. The AXL W451C mutation was not identified in any non-sarcoma malignancy. A review of publicly available data sets revealed a single AXL W451C-mutant case of UPS that clustered with MFS/UPS by methylation profiling. Functional studies revealed a novel activation mechanism: the W451C mutation causes abnormal unregulated dimerization of the AXL receptor tyrosine kinase through disulfide bond formation between pairs of mutant proteins expressing ectopic cysteine residues. This dimerization triggers AXL autophosphorylation and activation of downstream ERK signaling. We further report sarcomas of diverse histologic subtypes with AXL gene amplifications, with the highest frequency of amplification identified in MFS cases without the W451C mutation. In summary, the activating AXL W451C mutation appears highly specific to MFS, with a novel mechanism to drive unregulated signaling. Moreover, AXL gene amplifications and messenger RNA overexpression are far more frequent in MFS than in other sarcoma subtypes. We conclude that these aberrations in AXL are distinct features of MFS and may aid diagnosis, as well as the selection of available targeted therapies.

Update on immunohistochemistry in bone and soft tissue tumors: Cost-effectively replacing molecular testing with immunohistochemistry

Soft tissue tumors form part of a challenging domain in diagnostic pathology owing to their comparative rarity, astonishing histologic diversity, and overlap between entities. Many of these tumors are now known to be defined by highly recurrent, or, in some instances, unique molecular alterations. Insights from gene profiling continue to elucidate the wider molecular landscape of soft tissue tumors; many of these advances have been co-opted by immunohistochemistry (IHC) for diagnostic applications. There now exists a multitude of antibodies serving as surrogate markers of recurrent gene fusions, amplifications, and point mutations, which, in certain settings, can replace the need for more resource and time-intensive cytogenetic and molecular genetic analyses. IHC presents many advantages including rapid turnaround time, cost-effectiveness, and interpretative reproducibility. A sensible application of these immunohistochemical markers complemented by a working knowledge of the molecular pathogenesis of bone and soft tissue tumors permits accurate diagnosis in the majority of cases. In this review, we will outline some of these biomarkers while emphasizing molecular correlates and highlighting interpretative challenges and pitfalls.

Multitarget, multiagent PLGA nanoparticles for simultaneous tumor eradication and TME remodeling in a melanoma mouse model

Despite the fact that chemoimmunotherapy has emerged as a key component in the era of cancer immunotherapy, it is challenged by the complex tumor microenvironment (TME) that is jam-packed with cellular and non-cellular immunosuppressive components. The aim of this study was to design a nanoparticulate system capable of sufficiently accumulating in the tumor and spleen to mediate local and systemic immune responses, respectively. The study also aimed to remodel the immunosuppressive TME. For such reasons, multi-functional polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) were engineered to simultaneously eradicate the cancer cells, silence the tumor-associated fibroblasts (TAFs), and re-educate the tumor-associated macrophages (TAMs) using doxorubicin, losartan, and metformin, respectively. These agents were also selected for their ability to tip the balance of the splenic immune cells towards immunostimulatory phenotypes. To establish TAM and TAF cultures, normal macrophages and fibroblasts were incubated with B16F10 melanoma cell (Mel)-derived secretome. Drug-loaded PLGA NPs were prepared, characterized, and tested in the target cell types. Organ distribution of fluorescein-loaded PLGA NPs was evaluated in a mouse model of melanoma. Finally, the local and systemic effects of different combination therapy programs were portrayed. The in vitro studies showed that the drug-loaded PLGA NPs could significantly ablate the immunosuppressive nature of Mel and skew TAMs and TAFs towards more favorable phenotypes. While in vivo, PLGA NPs were proven to exhibit long blood circulation time and to localize preferentially in the tumor and the spleen. The combination of either metformin or losartan with doxorubicin was superior to the monotherapy, both locally and systemically. However, the three-agent combo produced detrimental effects in the form of compromised well-being, immune depletion, and metastasis. These findings indicate the potential of TME remodeling as means to prime the tumors for successful chemoimmunotherapy. In addition, they shed light on the importance of the careful use of combination therapies and the necessity of employing dose-reduction strategies. D-NPs doxorubicin-loaded NPs, M-NPs metformin-loaded NPs, L-NPs losartan-loaded NPs, TAMs tumor-associated macrophages, TAFs tumor-associated fibroblasts, PD-L1 programmed death ligand 1, TNF-α tumor necrosis factor alpha, TGF-β transforming growth factor beta, CD206/40/86 cluster of differentiation 206/40/86, α-SMA alpha-smooth muscle actin, MMPs matrix metalloproteases.

A rare case of cutaneous myxoma with trichofolliculoma-like features

Carney complex is a rare genetic disorder associated with a number of cutaneous lesions, especially cutaneous myxomas. We present a rare case of cutaneous myxoma (superficial angiomyxoma) with trichofolliculoma-like features in a patient with Carney complex, and explore how the associated histopathology provides critical context for elucidating the etiology of this benign neoplasm.

Superficial low-grade fibromyxoid sarcoma

BACKGROUND

Low-grade fibromyxoid sarcoma (LGFMS) typically involves deep soft tissue (beneath the fascia) of the proximal extremities and trunk. Long-term follow-up has shown a high rate of local recurrence, metastasis, and death. To the best of our knowledge, there is only one previous large series focusing on superficial LGFMS suggesting superficial tumors are disproportionately more common in children and may have a better prognosis. Our study's primary goals are to confirm these findings and increase general awareness that LGFMS may arise in superficial soft tissue.

METHODS

We retrieved our cases of superficial LGFMS diagnosed between 2008 and 2020. Available slides were reviewed, and clinical data and follow-up information were obtained.

RESULTS

The patients included nine males and 14 females with a median age of 29 years; eight (35%) were children (<18 years) and five (22%) were young adults (18-30 years). The majority involved the lower extremities (65%). The tumors were primarily centered in the subcutis (91%) and dermis (9%). Microscopically, they had typical features of LGFMS with alternating fibrous and myxoid zones composed of bland, slightly hyperchromatic spindled cells. All were positive for MUC4 by immunohistochemistry and/or FUS rearrangement by FISH. Follow-up on 14 cases ranged from 11 to 148 months (median 61 months) with no evidence of recurrences or distant metastases.

CONCLUSIONS

Compared to conventional deep-seated counterparts, superficial LGFMS is more likely to occur in the extremities of children and young adults and may have a better clinical outcome. Further studies with longer follow-up will likely help support these findings.

Oral soft-tissue myxoma

Oral soft-tissue myxomas of the oral cavity have been sparsely cited in the medical literature worldwide. This could be due to other clinically and/or histologically similar lesions requiring accurate differential diagnosis by experienced physicians and pathologists. Although myxomas are benign and do not metastasise, they have higher rates of recurrence and deserve proper attention and to be reported as well. Soft-tissue myxomas of the oral cavity are extremely rare and very few cases have been reported in the literature. The article describes a soft-tissue myxoma in a male patient in his 40s and review of published cases.

Myxoid Dermatofibrosarcoma Protuberans of the Scrotum: Rare Tumor in an Uncommon Location

Background

Case Presentation

Conclusion

Superficial Angiomyxomas Frequently Demonstrate Loss of Protein Kinase A Regulatory Subunit 1 Alpha Expression: Immunohistochemical Analysis of 29 Cases and Cutaneous Myxoid Neoplasms With Histopathologic Overlap

Superficial angiomyxomas (SAMs) are benign cutaneous tumors that arise de novo and in the setting of the Carney complex (CC), an autosomal dominant disease with several cutaneous manifestations including lentigines and pigmented epithelioid melanocytomas. Although most SAM do not pose a diagnostic challenge, a subset can demonstrate histopathologic overlap with other myxoid tumors that arise in the skin and subcutis. Traditional immunohistochemical markers are of limited utility when discriminating SAM from histopathologic mimics. Since protein kinase A regulatory subunit 1 alpha (PRKAR1A) genetic alterations underlie most CC cases, we investigated whether SAM demonstrate loss of PRKAR1A protein expression by immunohistochemistry. In our series, 29 SAM, 26 myxofibrosarcoma, 5 myxoid dermatofibrosarcoma protuberans, 11 superficial acral fibromyxomas, and 18 digital mucous cysts were characterized. Of the 29 SAM examined in this study, 1 was associated with documented CC in a 5-year-old girl. SAM tended to arise in adults (mean 49.7 y; range: 5 to 87 y). Loss of PRKAR1A was seen in 55.2% of cases (16/29) and had a male predilection (87.5%, 12/16). PRKAR1A-inactivated SAM demonstrated significant nuclear enlargement (100%, 16/16 vs. 23.1%, 3/13), multinucleation (81.3%, 13/16 vs. 23.1%, 3/13), and presence of neutrophils (43.8%, 7/16 vs. 0%, 0/13). In contrast, PRKAR1A was retained in all cases of myxofibrosarcoma (100%, 26/26), myxoid dermatofibrosarcoma protuberans (100%, 5/5), superficial acral fibromyxomas (100%, 11/11), and digital mucous cyst (100%, 18/18). Taken together, PRKAR1A loss by immunohistochemistry can be used as an adjunctive assay to support the diagnosis of SAM given the high specificity of this staining pattern compared with histopathologic mimics.

Fusion of the Genes PHF1 and TFE3 in Malignant Chondroid Syringoma

BACKGROUND/AIM

Malignant chondroid syringoma is a rare tumor of unknown pathogenesis.

MATERIALS AND METHODS

Genetic analyses were performed on a malignant chondroid syringoma.

RESULTS

G-banding analysis of short-term cultured tumor cells yielded the karyotype 46,Y,t(X;6)(p11;p21)[15]/46,XY[2]. RNA sequencing detected an in-frame fusion of PHF1 from 6p21 with TFE3 from Xp11, verified by RT-PCR and Sanger sequencing. Genomic PCR showed that the PHF1-TFE3 junction was identical to the fusion found by RNA sequencing and RT-PCR.

CONCLUSION

Malignant chondroid syringoma is genetically related to tumors with PHF1 rearrangements such as low-grade endometrial sarcoma and ossifying fibromyxoid tumor, but also with tumors having TFE3 rearrangements such as renal cell carcinoma, alveolar soft part sarcoma, PEComa, and epithelioid hemangioendothelioma. Further investigations on malignant chondroid syringomas are needed in order to determine whether genetic heterogeneity exists among them and the clinical impact of the PHF1-TFE3 fusion.

[Myxoid soft tissue tumours : An algorithm for differential diagnosis]

Soft tissue neoplasms with myxoid features are collectively not uncommon. Their often complex differential diagnosis makes them significantly over-represented among consultation cases. This applies not only to sarcomas but in particular to benign lesions as well. Generally, myxoid soft tissue lesions are divided into two major groups: (1) myxoid lesions by definition (which can however rarely be non-myxoid) and (2) rare myxoid variants of otherwise non-myxoid entities.Four major diagnostic challenges are responsible for the complexity of myxoid soft tissue neoplasms: (1) Diagnosis of malignancy in many cases is not based on conventional malignancy criteria but is defined by the entity itself, making under-diagnosis of malignancy likely in entities such as low-grade fibromyxoid sarcoma. (2) On the other hand, harmless myxoid lesions with features of high proliferation, e.g. nodular and proliferative fasciitis, tend to be over-diagnosed as malignant by the unworried. (3) The necessity to assess not only cellular morphology/differentiation, but also the stromal, vascular and architectural characteristics adds to the complexity of the differential diagnostic algorithm. (4) Last but not least, recognition of unexpected myxoid variants of non-myxoid entities is basically impossible if focal conventional areas are absent, underlining the need for high suspicion index and sufficient sampling.This review illuminates the various aspects related to the differential diagnostic workup of these challenging entities.