NTRK fusion cervical sarcoma: a report of three cases, emphasising morphological and immunohistochemical distinction from other uterine sarcomas, including adenosarcoma

Primary NTRK -rearranged Spindle Cell Neoplasm of the Gastrointestinal Tract: A Clinicopathological and Molecular Analysis of 8 Cases

NTRK-rearranged spindle cell neoplasm occurs predominantly in the superficial or deep soft tissues of extremities or trunk. Occurrence in the visceral organs is extremely rare. Herein, we describe 8 cases of NTRK-rearranged spindle cell neoplasm that arose primarily in the gastrointestinal tract. Patients included 5 males and 3 females with age at presentation ranging from 6 to 63 years (median: 29.5 years). Tumors occurred in the colon (n=3), small intestine (n=2), rectum (n=2), and stomach (n=1). Tumor size ranged from 3.5 to 9 cm (median: 5 cm). Morphologically, 4 tumors were low-grade, composed of haphazard or intertwining fascicles of spindle cells, with prominent interstitial collagen fibers and ring-like perivascular hyalinization being present in 2 tumors. The other 4 tumors were histologically high-grade sarcomas, consisting of sweeping fascicles of atypical spindle cells showing increased cellularity and brisk mitotic activity. Immunohistochemically, 6/6 cases (100%) showed diffuse and strong cytoplasmic staining of pan-TRK. Variable expression of TrkA, CD34, and S100 was noted in 5/5 (100%), 5/8 (62.5%), and 4/7 (57.1%) cases, respectively. Fluorescence in situ hybridization analysis showed NTRK1 rearrangement (n=7) and NTRK2 rearrangement (n=1). In cases with available materials, RNA sequencing identified LMNA::NTRK1 (n=3), TPM3::NTRK1 (n=2), and STRN::NTRK2 (n=1) fusions. At follow-up (range: 4 to 30 months; median: 12.5 months), 6 of 7 patients who underwent surgery had no evidence of disease at last follow-up. One patient was succumbed to the disease at 12 months despite adjunctive treatment with TRK inhibitor larotrectinib after surgery. One patient was treated with larotrectinib alone. He showed significant response at 7 months after treatment. NTRK-rearranged spindle cell neoplasm represents an exceptionally rare entity in the gastrointestinal tract. The presence of interstitial collagen fibers and ring-like perivascular hyalinization and co-expression of CD34 and S100 are diagnostic clues to low-grade neoplasms. However, high-grade sarcomas pose a considerable diagnostic challenge to pathologists owing to the lack of specific features. The final diagnosis relies on molecular assays. Patients with advanced disease may benefit from TRK inhibitor treatment.

The "Other" Uterine Mesenchymal Neoplasms: Recent Developments and Emerging Entities

Uterine mesenchymal neoplasms are a challenging group of tumors that often show overlapping morphologic features and immunohistochemical profiles. The increasing use of molecular testing in these tumors has enabled a better appreciation of their pathobiology, resulting in a wave of emerging neoplasms and improved characterization of ones previously considered exceptionally rare. Identification of specific molecular alterations has permitted targeted therapy options in tumors that were typically unresponsive to conventional therapies, as well as recognition that a subset can have a hereditary basis. This review will discuss the more "common" of the uncommon uterine mesenchymal neoplasms, including inflammatory myofibroblastic tumor, perivascular epithelioid cell tumor, uterine tumor resembling ovarian sex cord tumor, and embryonal rhabdomyosarcoma. This will be followed by an overview of emerging entities, including NTRK-rearranged uterine sarcoma, SMARCA4-deficient uterine sarcoma, KAT6B/A::KANSL1 fusion uterine sarcoma, and MEIS1::NCOA2/1 fusion sarcoma.

NTRK-rearranged spindle cell sarcoma of the uterine cervix with a novel NUMA1::NTRK1 fusion

NTRK-rearranged uterine sarcoma is a recently described entity that represents a subset of uterine sarcomas with distinct clinicopathological features. From a molecular point of view, this tumour is defined by NTRK gene rearrangement, resulting in overexpression or constitutive activation of Trk receptors. The presence of NTRK fusion is indicative of treatment response with a selective small-molecule inhibitor of the Trk kinases. Here, we report a case of an NTRK-rearranged sarcoma of the uterine cervix in a 43-year-old patient, measuring 80 mm in its largest dimension, with a novel NUMA1-NTRK1 fusion, not previously reported in NTRK-rearranged uterine sarcomas or other NTRK-rearranged tumours. The fusion, involving NUMA1 exon 14 (NM_006185.4) and NTRK1 exon 11 (NM_002529.4), was identified by next-generation sequencing (NGS) studies (FusionPlex Pan Solid Tumor v2 panel). Although the presence of NTRK fusion has been reported in a variety of neoplasms, a fusion involving NUMA1 (nuclear mitotic apparatus protein 1) and a tyrosine kinase partner has previously been reported in human neoplasms only in a handful of cases. The resulting fusion protein comprises the oligomerization domain of NUMA1, which is predicted to cause constant activation of the tyrosine kinase domain of NTRK1. The recognition and accurate diagnosis of these tumours are important due to the availability of potential targeted therapeutic options.

Efficient Identification of Patients With NTRK Fusions Using a Supervised Tumor-Agnostic Approach

CONTEXT.—

The neurotrophic tropomyosin receptor kinase (NTRK) family gene rearrangements have been recently incorporated as predictive biomarkers in a "tumor-agnostic" manner. However, the identification of these patients is extremely challenging because the overall frequency of NTRK fusions is below 1%. Academic groups and professional organizations have released recommendations on the algorithms to detect NTRK fusions. The European Society for Medical Oncology proposal encourages the use of next-generation sequencing (NGS) if available, or alternatively immunohistochemistry (IHC) could be used for screening with NGS confirmation of all positive IHC results. Other academic groups have included histologic and genomic information in the testing algorithm.

OBJECTIVE.—

To apply some of these triaging strategies for a more efficient identification of NTRK fusions within a single institution, so pathologists can gain practical insight on how to start looking for NTRK fusions.

DESIGN.—

A multiparametric strategy combining histologic (secretory carcinomas of the breast and salivary gland; papillary thyroid carcinomas; infantile fibrosarcoma) and genomic (driver-negative non-small cell lung carcinomas, microsatellite instability-high colorectal adenocarcinomas, and wild-type gastrointestinal stromal tumors) triaging was put forward.

RESULTS.—

Samples from 323 tumors were stained with the VENTANA pan-TRK EPR17341 Assay as a screening method. All positive IHC cases were simultaneously studied by 2 NGS tests, Oncomine Comprehensive Assay v3 and FoundationOne CDx. With this approach, the detection rate of NTRK fusions was 20 times higher (5.57%) by only screening 323 patients than the largest cohort in the literature (0.30%) comprising several hundred thousand patients.

CONCLUSIONS.—

Based on our findings, we propose a multiparametric strategy (ie, "supervised tumor-agnostic approach") when pathologists start searching for NTRK fusions.

Pan-TRK immunohistochemistry in gynaecological mesenchymal tumours: diagnostic implications and pitfalls

AIMS

NTRK-rearranged sarcomas of the female genital tract mainly occur in the uterus (more commonly cervix than corpus) and are characterized by a "fibrosarcoma-like" morphology and NTRK gene rearrangements. These neoplasms may exhibit histological overlap with other entities and can present diagnostic difficulties without molecular confirmation. Pan-TRK immunohistochemistry was developed to identify tumours harbouring NTRK rearrangements. The aim of this study was to characterize pan-TRK immunohistochemical expression in a large cohort of gynaecological mesenchymal neoplasms and investigate the utility of pan-TRK immunohistochemistry to distinguish NTRK-rearranged sarcoma from its mimics.

METHODS AND RESULTS

A total of 473 gynaecological mesenchymal tumours (461 without known NTRK fusions and 12 NTRK-rearranged sarcomas) were selected. Pan-TRK immunohistochemistry (EPR17341, Abcam) was performed on whole tissue sections and tissue microarrays. Molecular interrogation of pan-TRK positive tumours was performed by RNA sequencing or fluorescence in situ hybridization (FISH). Of the 12 NTRK-rearranged sarcomas, 11 (92%) exhibited diffuse (≥70%) cytoplasmic pan-TRK staining with moderate/marked intensity, while the other was negative. Eleven (2.4%) additional tumours also exhibited pan-TRK immunohistochemical expression: three low-grade endometrial stromal sarcomas, seven high-grade endometrial stromal sarcomas, and an undifferentiated uterine sarcoma. Molecular confirmation of the absence of NTRK rearrangements was possible in nine of these tumours. Of these nine neoplasms, seven exhibited focal/multifocal (<70%) pan-TRK cytoplasmic staining with weak/moderate intensity.

CONCLUSION

Even though pan-TRK immunohistochemical expression is not entirely sensitive or specific for NTRK-rearranged sarcomas, these neoplasms tend to exhibit diffuse staining of moderate/strong intensity, unlike its mimics. Pan-TRK should be performed in monomorphic uterine (corpus and cervix) spindle cell neoplasms that are negative for smooth muscle markers and hormone receptors and positive for CD34 and/ or S100. Ultimately, the diagnosis requires molecular confirmation.

[Diagnosis of uterine sarcomas and rare uterine mesenchymal tumours with malignant potential. Guidelines of the French Sarcoma Group and Rare Gynaecological Tumours]

The landscape of uterine sarcomas is becoming more complex with the description of new entities associated with recurrent driver molecular alterations. Uterine sarcomas, in analogy with soft tissue sarcomas, are distinguished into complex genomic and simple genomic sarcomas. Leiomyosarcomas and undifferentiated uterine sarcomas belong to complex genomic sarcomas group. Low-grade and high-grade endometrial stromal sarcomas, other rare tumors associated with fusion transcripts (such as NTRK, PDGFB, ALK, RET ROS1) and SMARCA4-deficient uterine sarcoma are considered simple genomic sarcomas. The most common uterine sarcoma are first leiomyosarcoma and secondly endometrial stromal sarcomas. Three different histological subtypes of leiomyosarcoma (fusiform, myxoid, epithelioid) are identified, myxoid and epithelioid leiomyosarcoma being more aggressive than fusiform leiomyosarcoma. The distinction between low-grade and high-grade endometrial stromal sarcoma is primarily morphological and immunohistochemical and the detection of fusion transcripts can help the diagnosis. Uterine PEComa is a rare tumor, which is distinguished into borderline and malignant, according to a risk assessment algorithm. Embryonal rhabdomyosarcoma of the uterine cervix is more common in children but can also occur in adult women. Embryonal rhabdomyosarcoma of the uterine cervix is almost always DICER1 mutated, unlike that of the vagina which is wild-type DICER1, and adenosarcoma which can be DICER1 mutated but with less frequency. Among the emerging entities, sarcomas associated with fusion transcripts involving the NTRK, ALK, PDGFB genes benefit from targeted therapy. The integration of molecular data with histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

Uterine Neurotrophic Tyrosine Receptor Kinase Rearranged Spindle Cell Neoplasms: Three Cases of an Emerging Entity

Uterine sarcomas are rare; most are either smooth muscle or endometrial stromal in origin. Recent molecular advances have identified several, genetically defined entities with specific morphologic, clinicopathological associations, and therapeutic options. We report 3 cases of uterine neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasms," currently classified as "emerging entities" in the WHO Classification of Female Genital Tract Tumors, 2020, Fifth Edition. The affected patients were 32, 34, and 42 years of age. Two patients presented with vaginal bleeding; the third presented with a cervical mass found incidentally during laparoscopy for an ectopic gestation. All 3 tumors were polypoid masses that distorted the cervix. Microscopically, they comprised cellular, fascicular, and storiform, plump spindle cells, with occasional rounded cells, and frequent mitoses (4-48/10 high power fields) in a myxoid stroma. All 3 cases showed entrapment of benign cervical glands. Inflammatory cell infiltrates, including plasma cells, were noted in all 3 tumors. One case had tumor cell necrosis, osteoid-like material, and osteoclast-like giant cells and showed lymphovascular invasion. Immunohistochemically, our cases showed patchy S100 (2/3) and CD34 (3/3) positivity. CD10 was positive in 2/3 cases. 3/3 cases showed pan-tropomyosin receptor kinase positivity (cytoplasmic). The NTRK-translocations demonstrated were: NTRK1::TMP3, NTRK1::TPR, and NTRK3::SPECC1L. Two of the patients had extensive disease and underwent chemotherapy. Larotrectinib was approved for one patient who demonstrated a striking reduction in tumor volume upon initiation of this treatment.

The Impact of ETV6-NTRK3 Oncogenic Gene Fusions on Molecular and Signaling Pathway Alterations

Chromosomal translocations creating fusion genes are common cancer drivers. The oncogenic ETV6-NTRK3 (EN) gene fusion joins the sterile alpha domain of the ETV6 transcription factor with the tyrosine kinase domain of the neurotrophin-3 receptor NTRK3. Four EN variants with alternating break points have since been detected in a wide range of human cancers. To provide molecular level insight into EN oncogenesis, we employed a proximity labeling mass spectrometry approach to define the molecular context of the fusions. We identify in total 237 high-confidence interactors, which link EN fusions to several key signaling pathways, including ERBB, insulin and JAK/STAT. We then assessed the effects of EN variants on these pathways, and showed that the pan NTRK inhibitor Selitrectinib (LOXO-195) inhibits the oncogenic activity of EN2, the most common variant. This systems-level analysis defines the molecular framework in which EN oncofusions operate to promote cancer and provides some mechanisms for therapeutics.

Targeted Treatment of Soft-Tissue Sarcoma

Background: Soft-tissue sarcoma (STS) is a heterogeneous group of sarcomas with a low incidence. The treatment of advanced disease is poor, and mortality is high. We aimed to generate an overview of the clinical experiences with targeted treatments based on a pre-specified target in patients with STS. Methods: A systematic literature search was conducted in PubMed and Embase databases. The programs ENDNOTE and COVIDENCE were used for data management. The literature was screened to assess the article's eligibility for inclusion. Results: Twenty-eight targeted agents were used to treat 80 patients with advanced STS and a known pre-specified genetic alteration. MDM2 inhibitors were the most-studied drug (n = 19), followed by crizotinib (n = 9), ceritinib (n = 8), and ⁹⁰Y-OTSA (n = 8). All patients treated with the MDM2 inhibitor achieved a treatment response of stable disease (SD) or better with a treatment duration of 4 to 83 months. For the remaining drugs, a more mixed response was observed. The evidence is low because most studies were case reports or cohort studies, where only a few STS patients were included. Conclusions: Many targeted agents can precisely target specific genetic alterations in advanced STS. The MDM2 inhibitor has shown promising results.

NTRK-rearranged spindle cell neoplasms: a clinicopathological and molecular study of 13 cases with peculiar characteristics at one of the largest institutions in China

NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) represent an emerging group of rare tumours defined using molecular means. To the best of our knowledge, there have been no large series of reports about this tumour in the Chinese population in English full-text articles. Herein, we present 13 NTRK-RSCNs with peculiar characteristics. Ten of the 13 (77%) patients were children without sex differences. The tumour locations included six trunks, four extremities, two recta, and one small bowel. The histological morphology included four lipofibromatosis-like neural tumour (LPF-NT)-like, eight malignant peripheral nerve sheath tumours (MPNST)/fibrosarcoma-like, and one extremely rare myxofibrosarcoma-like pattern. Immunohistochemically, all cases were CD34, pan-TRK and TRK-A positive, SOX-10 negative, and H3K27me3 intact. S-100 protein expression was identified in 11 of 13 (85%) cases. Genetically, NTRK1 rearrangements were considered positive (7/13, 54%) or suspicious for positivity (6/13, 46%) by fluorescence in situ hybridisation. Next-generation sequencing and Sanger sequencing confirmed NTRK1 fusions with a variety of partner genes, including five LMNA, three TPM3, one SQSTM1, three novel CPSF6, IGR (downstream PMVK), and GAS2L1 genes. Interestingly, the last tumour concurrently harboured a second EWSR1-PBX1 fusion, which has never been reported. Four patients developed local recurrence and two of them suffered metastasis. In our study, NTRK-RSCNs had peculiar fusions that displayed unusual or complicated clinicopathological features. Histological clues and IHC helped streamline a small subset of potential candidates. Although FISH is a powerful technology for identifying NTRK rearrangements, RNA-/DNA-based NGS is recommended for highly suspected cases in which FISH signal patterns are not discernible as classic positive patterns, particularly if targeted therapy is considered.

Case Report: A case of COL1A1–PDGFB fusion uterine sarcoma at cervix and insights into the clinical management of rare uterine sarcoma

COL1A1–PDGFB gene fusion uterine sarcoma is an especially rare malignant mesenchymal tumor that was previously classified as an undifferentiated uterine sarcoma due to the lack of specific features of differentiation. Till now, only five cases have been reported, and here we presented another case recently diagnosed in a Chinese woman who had vaginal bleeding. She presented with a cervical mass at the anterior lip of the cervix invading the vagina and was treated with laparoscopic total hysterectomy plus bilateral salpingo-oophorectomy (TH+BSO) and partial vaginal wall resection with the final pathology of COL1A1–PDGFB fusion uterine sarcoma. Our aim is to emphasize the importance of differential diagnosis of this rare tumor, as early precise diagnosis may allow patients to benefit from the targeted therapy imatinib. This article also serves as further clinical evidence of this disease, serving to increase clinical awareness of this rare sarcoma to avoid misdiagnosis.

Head and Neck Mesenchymal Tumors with Kinase Fusions: A Report of 15 Cases With Emphasis on Wide Anatomic Distribution and Diverse Histologic Appearance

Mesenchymal tumors harboring various kinase fusions were recently recognized as emerging entities mainly in the soft tissues. We herein investigate the clinicopathologic and molecular characteristics of head and neck mesenchymal tumors harboring kinase fusions. The study cohort included 15 patients with a median age of 13 years (ranging from congenital to 63 y). The kinase genes involved in descending order were NTRK1 (n=6), NTRK3 (n=5), BRAF (n=2), and 1 each with MET, and RET. The anatomic locations were broad involving all tissue planes, including skin (n=4), intraosseous (n=4), major salivary glands (n=2), sinonasal tract (n=2), soft tissue of face or neck (n=2), and oral cavity (n=1). The histologic spectrum ranged from benign to high grade, in descending order including tumors resembling malignant peripheral nerve sheath tumor (MPNST)-like, fibrosarcoma (infantile or adult-type), lipofibromatosis-like neural tumor (LPFNT), inflammatory myofibroblastic tumor-like, and a novel phenotype resembling myxoma. Perivascular hyalinization/stromal keloid-like collagen bands and staghorn vasculature were common features in MPNST-like and LPFNT-like tumors. Two tumors (1 each with NTRK1 or BRAF rearrangement) were classified as high grade. By immunohistochemistry, S100 and CD34 positivity was noted in 71% and 60%, frequently in MPNST-like and LPFNT-like phenotypes. Pan-TRK was a sensitive marker for NTRK-translocated tumors but was negative in tumor with other kinase fusions. One patient with a high-grade tumor developed distant metastasis. Molecular testing for various kinase fusions should be considered for S100+/CD34+ spindle cell neoplasms with perivascular hyalinization and staghorn vessels, as pan-TRK positivity is seen only in NTRK fusions.

Dramatic response to entrectinib in a patient with malignant peripheral nerve sheath tumor harboring novel SNRNP70-NTRK3 fusion gene

Neurotropic tropomyosin receptor kinase (NTRK) gene rearrangements have been reported in limited cases of sarcomas; however, to date, there has been only one report of such rearrangements in malignant peripheral nerve sheath tumors (MPNSTs). Herein, we describe a 51-year-old male patient with a buttock tumor arising from the sciatic nerve, which was diagnosed as MPNST with positive S-100 staining, negative SOX10 staining, and loss of trimethylation at lysine 27 of histone H3 (H3K27me3) confirmed by immunohistochemistry. Soon after the resection of the primary tumor, the patient was found to have pulmonary and lymph node metastases. Chemotherapy with eribulin and trabectedin showed limited effects. However, the patient responded rapidly to pazopanib, but severe side effects caused discontinuation of the treatment. RNA panel testing revealed a novel fusion gene between Small Nuclear Ribonucleoprotein U1 Subunit 70 (SNRNP70) gene and NTRK3 gene. Furthermore, loss of NF1, SUZ12, and CDKN2A genes was confirmed by DNA panel testing, which is compatible with a histological diagnosis of MPNST. SNRNP70 possesses a coiled-coiled domain and seems to induce constitutive activation of NTRK3 through dimerization. In fact, immunohistochemistry revealed diffuse staining of pan-TRK within tumor cells. Treatment with entrectinib, which is an NTRK inhibitor, showed a quick and durable response for 10 months. Although NTRK rearrangements are very rare in MPNST, this case highlights the importance of genetic testing in MPNST, especially using an RNA panel for the detection of rare fusion genes.

Mullerian adenosarcoma: clinicopathologic and molecular characterization highlighting recurrent BAP1 loss and distinctive features of high-grade tumors

Mullerian adenosarcoma is an uncommon mesenchymal tumor of the gynecologic tract. Most cases are low-grade, while high-grade adenosarcomas are rare and not well studied. Herein, we characterize the clinicopathologic and molecular features of 27 adenosarcomas of gynecologic origin, enriched for high-grade tumors subjected to targeted panel sequencing. Sarcomatous overgrowth was more frequently seen in high-grade compared to low-grade tumors (12/17, 71%, vs 1/10, 10%, p = 0.004) and heterologous elements were exclusive to high-grade cases (n = 7, p = 0.03). All deaths were from high-grade disease (advanced primary, n = 2, or recurrence, n = 5). Genetic alterations specific to high-grade adenosarcomas have known associations with chromosome instability, including TP53 mutations (n = 4) and amplifications of MDM2 (n = 2) and CCNE1 (n = 2). Somatic ATRX frameshift mutations were found in 2 patients with high-grade recurrences following a primary low-grade adenosarcoma and ATRX deletion in 1 high-grade adenosarcoma with an adjacent low-grade component. The fraction of genome altered by copy number alterations was significantly higher in high-grade compared to low-grade adenosarcomas (P = 0.001). Other recurrent genetic alterations across the entire cohort included BAP1 homozygous deletions (n = 4), DICER1 mutations (n = 4), ARID1A mutations (n = 3), TERT promoter mutations (n = 2) and amplification (n = 1), as well as alterations involving members of the PI3K and MAPK signaling pathways. One tumor harbored an ESR1-NCOA3 fusion and another had an MLH1 homozygous deletion. Immunohistochemical analysis for BAP1 revealed loss of nuclear expression in 6/24 (25%) cases, including all four tumors with BAP1 deletions. Notably, out of 196 mesenchymal neoplasms of gynecologic origin, BAP1 homozygous deletion was only found in adenosarcomas (P = 0.0003). This study demonstrates that high-grade adenosarcomas are heterogeneous at the molecular level and are characterized by genomic instability and TP53 mutations; ATRX loss may be involved in high-grade transformation of low-grade adenosarcoma; and BAP1 inactivation appears to be a specific pathogenic driver in a subset of adenosarcomas.

Uterine sarcomas and rare uterine mesenchymal tumors with malignant potential. Diagnostic guidelines of the French Sarcoma Group and the Rare Gynecological Tumors Group

The landscape of uterine sarcomas is becoming increasingly complex with the description of new entities associated with recurrent molecular alterations. Uterine sarcomas, as well as soft tissue sarcomas, can be distinguished into complex genomic sarcomas and simple genomic sarcomas. Leiomyosarcoma and pleomorphic type undifferentiated uterine sarcoma belong to the first group. Low-grade and high-grade endometrial stromal sarcomas, NTRK, COL1A1::PDGFB, ALK, RET, ROS1 associated sarcomas, and SMARCA4 deficient uterine sarcoma belong to the second group. Leiomyosarcoma is the most common uterine sarcoma followed by endometrial stromal sarcomas. Three different histologic subtypes of leiomyosarcomas are recognized with distinct diagnostic criteria and different clinical outcomes, the myxoid and epithelioid leiomyosarcomas being even more aggressive than the fusiform type. The distinction between low-grade and high-grade endometrial stromal sarcoma is based first on morphology and immunohistochemistry. The detection of fusion transcripts helps in the diagnosis. Definitely recognized as a separate entity, uterine PEComa is a rare tumor whose diagnostic criteria are being recently defined. Uterine PEComa has a specific algorithm stratifying the tumors into uncertain malignant potential and malignant tumors. Embryonal rhabdomyosarcomas of the uterine cervix are not restricted to children but can also be observed in adult women and are almost always DICER1 mutated, unlike embryonal rhabdomyosarcoma of the vagina which are DICER1wild-type, and adenosarcoma which can be DICER1 mutated but with less frequency. As sarcomas associated with fusion transcripts involving the NTRK, ALK, COL1A1::PDGFB genes can benefit from targeted therapy, systematic detection are now relevant especially for patients with high risk of relapse or in recurrent setting. The integration of molecular data with dedicated expert pathology review for histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

Data Set for Reporting of Uterine Malignant and Potentially Malignant Mesenchymal Tumors: Recommendations From the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) seeks to produce standardized, evidence-based protocols for the reporting of tumors with the aim of ensuring that all cancer reports generated worldwide will be of similar high quality and record the same elements. Herein, we describe the development of the data set for the reporting of uterine malignant and potentially malignant mesenchymal tumors by a panel of expert pathologists and a single clinician and provide the commentary and rationale for the inclusion of core and noncore elements. This data set, which incorporates the recent updates from the 5th edition of the World Health Organization Classification of Female Genital Tumors, addresses several subjects of debate including which mesenchymal tumors should be graded, how to document extent of invasion, mitotic counts, and the role of ancillary testing in tumor diagnosis and patient management. The inclusion of elements is evidence-based or based on consensus of the expert panel with clinical relevance being the guiding standard.

NTRK-Fusion Sarcoma of the Uterine Cervix: Report of 2 Cases With Comparative Clinicopathologic Features

NTRK1/2/3 rearrangements have been identified as oncogenic drivers in a variety of tumors including those in the uterine cervix, and rarely, the uterine corpus. We report 2 cases of cervical sarcoma with NTRK gene rearrangements. Case 1 was a 54-yr-old woman who presented with postmenopausal bleeding and a 5.4 cm friable mass in the cervix. Microscopic examination of the tumor revealed proliferation of epithelioid and spindle cells arranged in alternating hypercellular and hypocellular areas, with subtle fibrosarcoma-like features. Coagulative tumor cell necrosis and readily recognizable mitoses (up to 40 mitotic figures per 10 high-power fields) were identified. Case 2 was a 52-yr-old woman who presented with abnormal vaginal bleeding and a 1.3 cm cervical mass. The resected cervical tumor showed proliferation of spindled cells with fascicular and storiform growth pattern, infiltrating into the smooth muscle with entrapment of normal endocervical glands. The tumor cells displayed mild cytologic atypia and low mitotic activity (1 mitotic figure per 10 high-power fields). The mixed inflammatory infiltrate was seen throughout the lesion, mimicking morphology of inflammatory myofibroblastic tumor. Immunohistochemical staining for S100 and CD34 demonstrated variable expression in case 1 and uniformly diffuse positivity in case 2. The tumor cells in both cases were focally positive for CD10, Cyclin D1, ER, and PR, and negative for AE1/AE3, desmin, SOX10, HMB-45. RNA fusion analysis identified SPECC1L-NTRK3 gene rearrangements in case 1 and TPM3-NTRK1 in case 2; DNA-based mutational analysis also revealed CDKN2A/B homozygous deletion in case 1. Despite accumulating literature on NTRK fusion mesenchymal tumors in gynecologic pathology, these tumors are still rare and lack well-established morphologic diagnostic criteria. Diagnostic and clinical recognition of these tumors is critical given the potential patient benefit from targeted therapy.

Comparative effectiveness of larotrectinib versus entrectinib for the treatment of metastatic NTRK gene fusion cancers

Aim: To extrapolate clinical trial results to estimate and compare expected progression-free and overall life years (LYs) and quality-adjusted LYs (QALYs) for larotrectinib and entrectinib in patients with colorectal cancer (CRC), soft tissue sarcoma (STS) and brain metastases prior to treatment with larotrectinib or entrectinib. Methods: A naive direct comparison of larotrectinib versus entrectinib was made using partitioned survival modeling methods from clinical trial data. Results: Larotrectinib resulted in an additional 1.58 LYs (1.17 QALYs), 5.81 LYs (2.02 QALYs) and 1.01 LYs in CRC, STS and baseline brain metastases, respectively, compared with entrectinib. Conclusion: Larotrectinib provided life expectancy and QALY gains compared with entrectinib. Additional studies will be beneficial as more patients are treated and survival data develop to better inform comparative effectiveness results.

NTRK -Rearranged Uterine Sarcomas: Clinicopathologic Features of 15 Cases, Literature Review, and Risk Stratification

NTRK -rearranged uterine sarcomas are rare spindle cell neoplasms that typically arise in the uterine cervix of young women. Some tumors recur or metastasize, but features which predict behavior have not been identified to date. Distinguishing these tumors from morphologic mimics is significant because patients with advanced stage disease may be treated with TRK inhibitors. Herein, we present 15 cases of NTRK- rearranged uterine sarcomas, the largest series to date. Median patient age was 35 years (range: 16 to 61). The majority arose in the uterine cervix (n=14) and all but 2 were organ-confined at diagnosis. Tumors were composed of an infiltrative, fascicular proliferation of spindle cells and most showed mild-to-moderate cytologic atypia. All were pan-TRK positive by immunohistochemistry (13/13); S100 (11/13) and CD34 (6/10) were usually positive. RNA or DNA sequencing found NTRK1 (10/13) and NTRK3 (3/13) fusions with partners TPR , TPM3 , EML4 , TFG , SPECC1L , C16orf72 , and IRF2BP2 . Unusual morphology was seen in 2 tumors which were originally diagnosed as unclassifiable uterine sarcomas, 1 of which also harbored TP53 mutations. Follow up was available for 9 patients, of whom 3 died of disease. By incorporating outcome data of previously reported tumors, adverse prognostic features were identified, including a mitotic index ≥8 per 10 high-power fields, lymphovascular invasion, necrosis, and NTRK3 fusion. Patients with tumors which lacked any of these 4 features had an excellent prognosis. This study expands the morphologic spectrum of NTRK -rearranged uterine sarcomas and identifies features which can be used for risk stratification.

Primary NTRK-rearranged Spindle Cell Neoplasm of the Lung: A Clinicopathologic and Molecular Analysis of 3 Cases

Three cases of primary NTRK-rearranged spindle cell neoplasm of the lung with resemblance to those described in the somatic soft tissues are presented. The patients are 2 males and 1 female with age at presentation ranging from 31 to 45 years (mean, 36 y). All the 3 tumors were discovered incidentally during physical examinations. None of the patients had any prior history of mesenchymal neoplasms anywhere else. Computed tomography revealed intrapulmonary mass located in the right upper lobe, left upper lobe, and left lower lobe, respectively. All the patients underwent lobectomy. Grossly, the tumors were described as yellowish-white solid measuring in size between 1.2 and 1.8 cm (mean, 1.5 cm). Histologically, they were characterized by monomorphic spindle cells arranged in haphazard fascicles accompanied by variable stromal collagens. Nuclear atypia was mild and mitotic activity was scarce. By immunohistochemistry, the neoplastic cells in all 3 cases showed strong and diffuse staining of CD34, pan-TRK, and TrkA with variable expression of S100 protein, whereas they were negative for cytokeratin, SOX10, ALK, α-smooth muscle actin, desmin, and STAT6. Fluorescence in situ hybridization analysis revealed NTRK1 rearrangement in all 3 cases. Subsequent next-generation sequencing identified TPM3-NTRK1 fusion in 2 cases and LMNA-NTRK1 fusion in 1 case. All 3 patients are alive without the disease (median follow-up, 9 mo; range, 4 to 87 mo). The cases present herein demonstrate that NTRK-rearranged spindle cell neoplasms may occur primarily in the lung, albeit extremely rare, and should be included in the differential diagnosis of primary pulmonary spindle cell neoplasms.

Adult NTRK-rearranged spindle cell neoplasms of the viscera: with an emphasis on rare locations and heterologous elements

NTRK-rearranged mesenchymal neoplasms mostly affect the soft tissues of pediatric patients. Given the responsiveness to selective NTRK inhibitors, it remains critical to identify those ultra-rare cases occurring in the viscera of adults. In five females and two males aged 18-53 years, we characterized visceral mesenchymal tumors harboring TPM3-NTRK1 [uterine cervix (N = 2), pleura, prostate], LMNA-NTRK1 (lung), SQSTM1-NTRK3 (heart), and NTRK3 rearrangement with unknown fusion partner (colon/mesocolon) with RNA sequencing, FISH, RT-PCR, and immunohistochemistry. The tumors exhibited spindled to ovoid/epithelioid or pleomorphic cells, often arranged in fascicles, and were low-to-intermediate-grade and high-grade in three and four cases, respectively. Keloid-like stromal collagen and perivascular hyalinization was noted in five. Adenosarcoma-like appearances were observed in two, manifesting frond-like protrusions in one cervical tumor and phyllodes-like architecture in the prostatic tumor. Abrupt high-grade transformation into pleomorphic liposarcoma was found in another cervical tumor, while the pleural tumor contained intermixed rhabdomyoblasts. Pan-TRK immunostaining was positive in all cases. All cases expressed CD34, while five were S100-positive. CDKN2A homozygous deletion with concomitant p16 loss occurred in 4/7. Whole-exome sequencing identified TP53 mutation (c.672+2T>C, involving a splice site, with concomitant protein loss) in a cervical sarcoma, limited to its heterologous liposarcomatous component. At least moderate pan-TRK immunoreactivity was present in varying proportions of potential pathologic mimics, with BCOR-positive sarcoma (56%, 5/9), undifferentiated uterine sarcoma (50%, 3/6), and spindle cell/sclerosing rhabdomyosarcoma (33%, 2/6) being among the most frequent. This underscored the unsatisfactory specificity of pan-TRK immunohistochemistry and warranted molecular confirmation in the diagnosis of adult NTRK-rearranged visceral mesenchymal neoplasms. The current report highlights the ever-expanding clinicopathologic and genetic spectrum of this entity by describing the unprecedented cardiac and pleural locations and heterologous differentiation, as well as the second NTRK-rearranged "prostatic stromal sarcoma," while substantiating CDKN2A deletion as a frequent occurrence.

NTRK Fusions in a Sarcomas Series: Pathology, Molecular and Clinical Aspects

Targeting molecular alterations has been proven to be an inflecting point in tumor treatment. Especially in recent years, inhibitors that target the tyrosine receptor kinase show excellent response rates and durable effects in all kind of tumors that harbor fusions of one of the three neurotrophic tyrosine receptor kinase genes (NTRK1, NTRK2 and NTRK3). Today, the therapeutic options in most metastatic sarcomas are rather limited. Therefore, identifying which sarcoma types are more likely to harbor these targetable NTRK fusions is of paramount importance. At the moment, identification of these fusions is solely based on immunohistochemistry and confirmed by molecular techniques. However, a first attempt has been made to describe the histomorphology of NTRK-fusion positive sarcomas, in order to pinpoint which of these tumors are the best candidates for testing. In this study, we investigate the immunohistochemical expression of pan-TRK in 70 soft tissue and bone sarcomas. The pan-TRK positive cases were further investigated with molecular techniques for the presence of a NTRK fusion. Seven out of the 70 cases showed positivity for pan-TRK, whereas two of these seven cases presented an NTRK3 fusion. Further analysis of the fused sarcomas revealed some unique histological, molecular and clinical findings. The goal of this study is to expand the histomorphological spectrum of the NTRK-fused sarcomas, to identify their fusion partners and to correlate these parameters with the clinical outcome of the disease. In addition, we evaluated the immunohistochemical expression pattern of the pan-TRK and its correlation with the involved NTRK gene.

Update on Mesenchymal Lesions of the Lower Female Genital Tract

This article provides an update of the recent developments in mesenchymal tumors of lower genital tract. We focus on the characterization of recurrent molecular events in certain genital stromal tumors, for instance angiomyofibroblastomas and superficial myofibroblastomas. Moreover, fusions involving Tyrosine-kinases receptors (NTRK, FRFR1, RET, COL1A1-PDGFB) have been demonstrated in an emerging group of mesenchymal tumors characterized by a fibrosarcoma-like morphology and a predilection for uterine cervix of premenopausal women. We also cover the topic of smooth muscle tumors of the lower genital tract, which can be now classified using the same diagnostic criteria than their uterine counterpart..

EML4-NTRK3 Fusion Cervical Sarcoma: A Case Report and Literature Review

The concept of neurotrophic factor tyrosine kinase receptor (NTRK) fusion tumor has emerged in recent years. Moreover, NTRK fusion is unusual in common tumors but can often be identified in rare tumors. The NTRK fusion cervical or uterine tumors are mainly recognized through case reports due to their extremely low incidence. In this study, we reported a new case of EML4–NTRK3 fusion cervical sarcoma to enhance its recognition. To the best of our knowledge, this is the first case from a Chinese institution. We also conducted a literature review, in which a total of 19 cases of NTRK fusion cervical tumors and 4 cases of uterine tumors were retrieved. We summarized the clinicopathological features, treatment methods, and prognosis of these cases. Based on available information, we observed that surgery and complete excision, if possible, are still the primary modes of therapy. In addition, an increasing number of studies have shown that tropomyosin receptor kinases (TRK) inhibitors can improve the prognosis of cancer patients with NTRK gene fusion, which gives a silver lining for patients with metastatic lesions. We found that age and mitotic rate may be associated with recurrence or metastasis by univariate survival analysis. To draw more convincing conclusions, there is a need to establish an international database of rare cases and aggregate these sporadic cases.

[Endometrial and other rare uterine sarcomas : Diagnostic aspects in the context of the 2020 WHO classification]

Uterine sarcomas are a heterogeneous group of rare malignancies. Mostly (40-50%), they are leiomyosarcomas, followed by endometrial stromal sarcomas (ESS), low-grade (LG) and high-grade (HG), as well as undifferentiated sarcoma of the uterus (UUS) and adenosarcomas (AS). Other, non-organ-specific tumours such as NTRK-rearranged spindle cell neoplasia, perivascular epithelioid cell tumour (PEComa) and inflammatory myofibroblastic tumour (IMT) are extremely difficult to differentiate.In the most recent WHO classification, endometrial stromal tumours are subdivided as follows: benign, expansively growing endometrial stromal nodule (ESN) with sharp demarcation, the histologically similar-looking LG-ESS with infiltrative growth, the highly malignant HG-ESS and, as a diagnosis of exclusion, the highly aggressive UUS lacking specific lines of differentiation. LG-ESS can be differentiated from HG-ESS in most cases histomorphologically and immunohistochemically, but molecular investigations are necessary in individual cases. HG-ESS can be divided into 4 subtypes (YWHAE/NUTM2 fusion low-grade component, YWHAE/NUTM2 fusion high-grade component, ZC3H7B-BCOR fusion or BCOR-ITD) on the basis of molecular findings. Prognostically unfavourable factors in AS are severe sarcomatous overgrowth, deep myometrial invasion, high-grade histology and lymphatic vessel invasion. Tumours with NTRK fusion are immunohistochemically positive for S100 and TRK. PEComas express cathepsin K and HMB45, as well as TFE3 when translocation is present. Almost every IMT shows an alteration in the ALK gene In the case of overlapping morphology and simultaneous therapeutic and prognostic relevance, it is becoming increasingly important to verify or confirm the suspected histomorphological diagnosis by immunohistochemical and possibly molecular investigations.

Nonsquamous Lesions of the Vulvar Skin and Subcutaneous Tissue: A Review (Part 2)

OBJECTIVE

The aim of this second article was to complete part 1 review of nonsquamous lesions of the vulvar skin and subcutaneous tissue (Journal of Lower Genital Tract Disease, 2021), clinically and pathologically, based on the fifth edition of the World Health Organization tumor classification.

MATERIALS AND METHODS

A database search of PubMed and Google Scholar was performed between 1970 and 2021, using the search terms "vulva," "lower genital tract," and "non-squamous lesions." The search was limited to "human gynecological pathology." Full article texts were reviewed, and reference lists were screened for additional articles. We excluded abstracts and articles written in the non-English language.

RESULTS

An initial list of 400 articles was identified. Thirty-seven articles discussed clinicopathological features of nonsquamous lesions of the vulvar skin and subcutaneous tissue.

CONCLUSIONS

Clinicopathological features of nonsquamous lesions of the vulvar skin and subcutaneous tissue as categorized by the updated World Health Organization classification are presented.

Expanding the Spectrum of Adult NTRK3-Rearranged Spindle Cell Neoplasms: A Recurrent NTRK3-SQSTM1 Fusion Spindle Cell Tumor With Deceptively Bland Morphology

OBJECTIVES

NTRK-rearranged spindle cell neoplasms (other than infantile fibrosarcoma) are an emerging entity of tumors that demonstrate wide variation in clinical and histopathologic features. We report a case of an NTRK-rearranged spindle cell neoplasm bearing a deceptively bland morphology.

METHODS

We performed histopathologic, immunohistochemical, and molecular evaluation on resection tissue. We also conducted a literature review on adult NTRK3-rearranged spindle cell neoplasms.

RESULTS

The tumor presented as a recurrent ankle mass in an elderly patient. Histologically, it was composed of bland spindle cells set in a fibrous to edematous stroma. Blood vessels were interspersed with subtle perivascular hyalinization and scattered lymphoid aggregates. Immunohistochemically, the spindle cells expressed CD34 and S100 while being negative for SOX10. The tumor also showed cytoplasmic reactivity for pan-tyrosine receptor kinase immunohistochemistry. Next-generation sequencing identified an NTRK3-SQSTM1 fusion. To the best of our knowledge, this fusion pair has not been previously reported in adult NTRK-rearranged mesenchymal tumors.

CONCLUSIONS

Altogether, this rare and diagnostically challenging case of an NTRK3-rearranged spindle cell tumor with low-grade morphology is in contrast to many of the reported adult NTRK3-rearranged mesenchymal tumors. Recognition of low-grade NTRK-rearranged tumors demands close attention to clues in morphology and immunoprofiles.

A rare case of recurrent ovarian cancer with TPM3‑NTRK1 gene rearrangement: A case report

NTRK gene fusion is rare in gynecological cancer. Entrectinib is a novel targeted drug, which is a potent inhibitor of TRK A, B and C. The present case report described a case of recurrent ovarian cancer with TPM3-NTRK1 rearrangement, which was detected by next-generation sequencing (NGS) and treated with entrectinib. A 56-year-old woman was diagnosed as having stage IV ovarian cancer with positive pleural fluid cytology. Neoadjuvant chemotherapy and interval debulking surgery, followed by chemotherapy, were performed. A total of 10 months after completion of chemotherapy, the disease recurred and the patient was treated with multimodal therapy for recurrence. DNA-based NGS detected TPM3-NTRK1 rearrangement and entrectinib therapy was initiated; however, the disease progressed despite 6 weeks of entrectinib administration, and 1 month after discontinuation of entrectinib, the patient died. After their death, immunohistochemistry with a pan-Trk monoclonal antibody was performed to determine the expression levels of TRK; however, immunohistochemistry was negative for TRK. In conclusion, the present case report described a rare case of recurrent ovarian cancer with TPM3-NTRK1 gene fusion, in which entrectinib was not effective. While NTRK gene fusion was detected by DNA-based NGS, immunohistochemistry was negative for TRK. These findings indicated that immunohistochemistry may be required for confirmation of TRK protein expression prior to entrectinib administration.

PD-L1, Mismatch Repair Protein, and NTRK Immunohistochemical Expression in Cervical Small Cell Neuroendocrine Carcinoma

Background

Cervical small cell neuroendocrine carcinoma (SCNC) is a rare and aggressive disease that lacks a standard treatment strategy or effective methods of targeted therapy. PD-L1 inhibitors for DNA mismatch repair system-deficient (dMMR) tumors and neurotrophin receptor tyrosine kinase (NTRK) inhibitors offer potential pan-cancer treatments.

Methods

Immunohistochemistry was employed as the main detection method, and any NTRK positive cases, identified by immunohistochemistry, were further submitted for evaluation by fluorescence in situ hybridization (FISH) and real-time polymerase chain reaction (RT-PCR) methods.

Results

Forty-six patients were enrolled. Positive PD-L1 expression was seen in 22 of the 43 patients (51.16%) with an average combined positive score of 6.82. PD-L1-positive patients were more likely to have a higher proliferation rate in the tumor, and they experienced less recurrence and death (p = 0.048 and 0.033, respectively) compared with the patients with negative PD-L1 expression. However, in the multivariate analysis, none of the clinical parameters was associated with the expression of PD-L1. There was no association between PD-L1 expression and disease recurrence or overall survival in the Kaplan-Meier analysis. All cases were found to be MMR-stable and lacked NTRK gene fusion. However, pan-Trk expressed in 14 (32.56%) of the 43 tested cases, but FISH and RT-PCR failed to confirm any positive fusion signals in IHC-positive cases.

Conclusions

PD-L1 may be an effective therapeutic target for cervical SCNC. Cervical SCNC is a MMR-stable tumor and lacks NTRK gene fusion. IHC isn’t a reliable method in the detection of NTRK gene fusion in cervical SCNC.

NTRK-Rearranged soft tissue neoplasms: A review of evolving diagnostic entities and algorithmic detection methods

The spectrum of tumors with NTRK1/2/3 rearrangements has expanded with widespread use of next generation sequencing (NGS) technology. For many years it was known that a majority of infantile fibrosarcomas (IFS), and their counterpart in the kidney, cellular congenital mesoblastic nephroma, contain the recurrent ETV6-NTRK3 fusion. Sequencing RNA transcripts from IFS and their morphologically similar counterparts in older children and adults has shown rearrangements with other 5' partners combined with NTRK1, NTRK2, and NTRK3 can also occur. For those tumors occurring outside of the infant age group, this has resulted in a proposed new diagnostic entity of "NTRK-rearranged spindle cell neoplasm." The clinical behavior of NTRK rearranged soft tissue tumors varies, though most show localized disease with rare metastases. The pathology of NTRK rearranged tumors exists on a spectrum, with overlapping features of classic infantile fibrosarcoma, lipofibromatosis, and malignant peripheral nerve sheath tumor. In this tumor spectrum, clinical and pathologic predictive factors are largely still to be determined, with no clear association between histologic grade and severity of disease. Of critical importance is detection of the NTRK rearrangement in order to guide treatment in patients with unresectable and metastatic disease. While resection is the definitive treatment, these tumors do show response to targeted TRK kinase inhibitors. Multiple detection methods are available, including immunohistochemistry, FISH, and next generation sequencing, which each have their merits and potential pitfalls. We aim to review the clinical characteristics and histomorphology of mesenchymal tumors with NTRK rearrangements as well as discuss molecular detection methods and diagnostic algorithms specific for soft tissue tumors.

Novel fusion sarcomas including targetable NTRK and ALK

BACKGROUND

Challenging emerging entities with distinctive molecular signatures may benefit from algorithms for diagnostic work-up.

METHODS

Fusion sarcomas (2020-2021, during pandemic) were diagnosed by clinicoradiology, morphology, phenotype, and next-generation sequencing (NGS).

RESULTS

Six fusion sarcomas in two males and four females involved the chest-wall, neck, or extremities; ages ranged 2-73, median 18 years. Sizes ranged 5.3-25.0, median 9.1 cm. These include high grade 1) TPR-NTRK1 of proximal femur with a larger rounded soft tissue mass, previously considered osteosarcoma yet without convincing tumor matrix. A pathologic fracture necessitated emergency hemipelvectomy (NED) and 2) novel KANK1-NTRK2 sarcoma of bone and soft tissue with spindled pleomorphic to epithelioid features (AWD metastases). 3) Novel ERC1-ALK unaligned fusion, a low grade infiltrative deep soft tissue hand sarcoma with prominent-vascularity, myopericytoid/lipofibromatosis-like ovoid cells, and collagenized stroma, was successfully treated with ALK-inhibitor (Crizotinib), avoiding amputation. These NTRK and ALK tumors variably express S100 and CD34 and were negative for SOX10. 4) and 5) CIC-DUX4 round cell tumors (rapid metastases/demise), one with COVID superinfection, were previously treated as Ewing sarcoma. These demonstrated mild pleomorphism and necrosis, variable myxoid change and CD99 reactivity, and a distinctive dot-like-Golgi WT1 immunostaining pattern. 6) A chest wall/thoracic round cell sarcoma, focal CD34/ keratins/CK7, revealed nuclear-STAT6, STAT6-NAB2 by NGS, confirming malignant solitary fibrous tumor, intermediate-risk-stratification (AWD metastases).

CONCLUSIONS

Recent fusion sarcomas include new KANK1-NTRK2 and ERC1-ALK, the latter successfully treated by targeted-therapy. ALK/NTRK fusion partners TPR and KANK1 suggest unusual high-grade morphology/behavior. Clinicoradiologic, morphologic, and phenotypic algorithms can prompt molecular-targeted immunostains or NGS for final classification and promising inhibitor therapy.

Primary Synovial Sarcoma of the Uterine Cervix: First Case Report

Synovial sarcoma is a translocation associated soft tissue malignancy frequently affecting young adults. The classic translocation is t(X;18)(p11.2;q11.2): SS18-SSX1/2/4 fusion. Synovial sarcoma tends to favor the distal extremities but can also arise in other locations. To date, no case of primary synovial sarcoma of the uterine cervix has been reported. We report a 42-yr-old woman with no prior history who presented to clinic with vaginal spotting for 3 mo and was found to have a large mass in the uterine cervix. The mass was evacuated from the vagina and sent for pathologic diagnosis. Sections showed proliferation of monotonous spindle cells with scant eosinophilic cytoplasm, round to slightly irregular nuclei, variable nucleoli and frequent mitosis in a background of delicate capillary and occasional thick-walled vessels. No malignant epithelium was identified in the entire specimen. On immunohistochemical workup tumor cells were negative for pan cytokeratin, OSCAR, EMA, chromogranin, S100, SMA, desmin, myogenin, WT1, CD117, CD34, and BRG1. CD45 was positive in a few inflammatory cells. Cyclin D1 showed partial weak to moderate nuclear reactivity. CD99 demonstrated strong diffuse membranous reactivity and BCL-2 showed strong cytoplasmic staining in 60% of tumor cells. Florescence in situ hybridization results for EWSR1, BCOR, and CIC gene rearrangements were negative, however, florescence in situ hybridization results for SS18 (SYT) (18q11) gene rearrangement was positive. A diagnosis of monophasic synovial sarcoma was rendered. We review the differential diagnoses of tumors with similar morphology and discuss the diagnostic process. With this case report it is imperative to include synovial sarcoma in differential diagnosis list of sarcomas of uterus and cervix.

Case report: NTRK1-rearranged cervical sarcoma with fibrosarcoma like morphology presenting in a 13-year-old managed with a neo-adjuvant TRK-inhibitor and surgical excision

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NTRK fusion-positive fibrosarcoma like tumour of the cervix in a paediatric patient.

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Fertility sparing surgery achieved with the use of a neo-adjuvant TKi.

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Identifying NTRK fusions may afford conservative treatment options in these tumours.

This case report reviews the case of a 13-year-old patient who presented with a 9 cm NTRK1-rearranged cervical sarcoma with fibrosarcoma like morphology. At presentation the lesion filled her vagina and pelvis and any attempt at surgical removal would have been morbid and led to loss of fertility. These neoplasms are extremely rare with 18 cases of the uterine cervix reported in the literature, none of which have occurred in a paediatric patient, and none of whom have received neo-adjuvant therapy prior to excision. Based upon evidence that has shown good tolerability and responses of paediatric NTRK fusion-positive solid tumours to TRK inhibitors, both in the neo-adjuvant and upfront setting, this patient was managed with neo-adjuvant entrectinib. Following a dramatic reduction in tumour size confirmed by imaging, she underwent conservative fertility sparing surgery with final histopathology showing no residual disease.

Low-grade Endometrial Stromal Sarcoma With Sex Cord-like Differentiation and PHF1-JAZF1 Fusion With Deletions: A Diagnostic Pitfall of JAZF1 FISH

The molecular knowledge on endometrial stromal neoplasms has been rapidly increasing and is considered complementary to morphologic and immunohistochemical findings for better categorization of these tumors. The most common molecular alteration observed in low-grade endometrial stromal sarcomas is the JAZF1-SUZ12 fusion, whereas, low-grade endometrial stromal sarcoma with sex cord-like differentiation have been shown more commonly to have fusions involving PHF1. Herein, we present a low-grade endometrial stromal sarcoma with sex cord-like differentiation with a fluorescence in situ hybridization showing the apparent loss of one copy of JAZF1 5' and 3' signals, rather than the expected "break-apart" pattern seen in the setting of a JAZF1 fusion. The case was then further evaluated by chromosome microarray and RNA fusion analysis. Overall, the molecular findings supported a PHF1-JAZF1 fusion with deletions right before and after the JAZF1 locus, impairing probe binding and resulting in the unusual "deletion" pattern observed in the JAZF1 fluorescence in situ hybridization, which would not intuitively suggest a fusion involving JAZF1. This case illustrates the importance of integration of morphological and molecular findings as well as the limitations of fluorescence in situ hybridization in detecting fusions, particularly in the setting of more complex chromosomal alterations even though the fusion partners are well-known.

Advances in understanding the molecular pathology of gynecological malignancies: the role and potential of RNA sequencing

For many years technological limitations restricted the progress of identifying the underlying genetic causes of gynecologicalcancers. However, during the past decade, high-throughput next-generation sequencing technologies have revolutionized cancer research. RNA sequencing has arisen as a very useful technique in expanding our understanding of genome changes in cancer. Cancer is characterized by the accumulation of genetic alterations affecting genes, including substitutions, insertions, deletions, translocations, gene fusions, and alternative splicing. If these aberrant genes become transcribed, aberrations can be detected by RNA sequencing, which will also provide information on the transcript abundance revealing the expression levels of the aberrant genes. RNA sequencing is considered the technique of choice when studying gene expression and identifying new RNA species. This is due to the quantitative and qualitative improvement that it has brought to transcriptome analysis, offering a resolution that allows research into different layers of transcriptome complexity. It has also been successful in identifying biomarkers, fusion genes, tumor suppressors, and uncovering new targets responsible for drug resistance in gynecological cancers. To illustrate that we here review the role of RNA sequencing in studies that enhanced our understanding of the molecular pathology of gynecological cancers.

Neurofibrosarcoma Revisited: An Institutional Case Series of Uterine Sarcomas Harboring Kinase-related Fusions With Report of a Novel FGFR1-TACC1 Fusion

Uterine sarcomas with variable CD34 and S100 expression represent an emerging class of tumor in the female genital tract which commonly presents in the endocervix of premenopausal women. Initial molecular characterization identified NTRK1 and NTRK3 gene fusions as oncogenic drivers in these tumors; however, the repertoire of genetic alterations is likely more diverse given the recent discovery of PDGFB and RET gene fusions in similarly described tumors. Importantly, these fusion events lead to the aberrant activation of kinases that are potentially therapeutically targetable; therefore, recognizing this class of tumor becomes critical for initiating the molecular testing required for an accurate diagnosis and identification of clinically actionable fusions. Here, we report our institutional experience with 12 cases of uterine spindle cell sarcomas harboring kinase-related fusions. Patients ranged from 21 to 80 years old (median, 38 y) and presented either asymptomatically or with pelvic pain and/or uterine bleeding. Eleven (92%; 11/12) tumors were localized to the cervix and 1 (8%; 1/12) tumor was localized in the anterior fundus of the uterine corpus. Tumors ranged in size from 1.5 to 15.0 cm (median, 6.0 cm) and were histologically characterized by a moderately cellular, infiltrative proliferation of spindle cells with features of benign gland entrapment, stromal collagen deposition, perivascular hyalinization, occasionally myxoid stroma, a lymphocytic infiltrate, occasional nuclear pseudoinclusions, and a pseudophyllodes architecture. RNA-sequencing identified NTRK1 (8/12), NTRK3 (1/12), and PDGFB (2/12) gene fusions, which have been previously implicated in this tumor class, as well as a novel FGFR1-TACC1 (1/12) fusion. All tumors in this cohort showed coexpression of CD34 and S100 by immunohistochemistry except for those tumors with PDGFB fusions which showed solely CD34 expression. Of the 10 surgically resected tumors with follow-up, outcomes best correlated with the stage of disease. One of 4 patients with stage IA tumors (1/4) had recurrences, half of the stage IB (2/4) tumors had recurrences and all of the stage IIB tumors (2/2) had recurrences and died of disease. Future studies are still required to better understand the spectrum of genetic alterations as well as evaluate the efficacy of targeted kinase inhibitors in this class of tumor.

[How to test for NTRK gene fusions: A practical approach for pathologists]

The recent availability of targeted anti-TRK therapies represents a new opportunity to treat patients with advanced cancers harboring NTRK gene fusions. In this article, we present an update on the practical modalities of implementing a "NTRK testing" to search for these fusions in view of the performances and availability of the different testing methods and the epidemiological characteristics of the tumors liable to present the NTRK1, NTRK2 or NTRK3 gene fusions.

Molecular Profiling Reveals Limited Targetable Biomarkers in Neuroendocrine Carcinoma of the Cervix

Neuroendocrine carcinoma of the cervix (NEC) is a rare and highly aggressive cervical malignancy. Given that no targeted therapy has been approved specifically to NEC, we investigated the presence of novel, potentially targetable biomarkers in a large cohort of NEC. Sixty-two NEC were molecularly profiled for biomarkers of targeted therapies including antibody-drug conjugates [delta-like canonical notch ligand 3 (DLL3), a trophoblast cell surface antigen 2 (TROP-2), and folate receptor 1 (FOLR1)], NTRK1-3 gene fusions, and immune checkpoint inhibitors [programmed death-ligand 1 (PD-L1), tumor mutational burden, and microsatellite instability] using immunohistochemistry and DNA/RNA next-generation sequencing assays. A cohort of squamous cell carcinomas of the cervix (n=599) was used for comparison for immune-oncology biomarkers. DLL3 expression was observed in 81% of the cases. DLL3 expression was inversely correlated with commonly observed pathogenic mutations in PIK3CA (17%) (P=0.018) and PTEN (10%) (P=0.006). Other more frequently seen pathogenic mutations (TP53 17%, KRAS 11%, and CTNNB1 5%) were not associated with DLL3 expression. TROP-2 expression was detected in only 1 case and no case expressed FOLR1. Although NTRK protein expression was observed in 21% of the cases, none of these had an NTRK gene fusion. PD-L1 expression (10%) and high tumor mutational burden (3%) were significantly less frequent in NEC compared with the squamous cell carcinoma cohort (79% and 11%, respectively). None of the NEC exhibited high microsatellite instability status. Despite frequent DLL3 expression in NEC, a potential therapeutic benefit of DLL3-targeted drugs remains uncertain given the recent failure of the Rova-T therapeutic trial in small cell lung carcinomas. Small cohorts of NEC enriched in PIK3CA/PTEN/AKT and programmed cell death protein 1/PD-L1 alterations indicate therapeutic roles for their respective inhibitors.

NTRK Fusions in Sarcomas: Diagnostic Challenges and Clinical Aspects

Tropomyosin receptor kinase (TK) is encoded by the neurotrophic tyrosine receptor kinase genes (NTRK) 1, 2, and 3, whose activation plays an important role in cell cycle proliferation and survival. Fusions of one of these genes can lead to constitutive activation of TRK, which can potentially be oncogenic. NTRK fusions are commonly present in rare histologic tumor types. Among sarcomas, infantile fibrosarcoma shows NTRK fusion in more than 90% of the cases. Many other sarcoma types are also investigated for NTRK fusions. These fusions are druggable alteration of the agnostic type, meaning that all NTRK fused tumors can be treated with NTRK-inhibitors regardless of tumor type or tissue of origin. TRK-inhibitors have shown good response rates, with durable effects and limited side effects. Resistance to therapy will eventually occur in some cases, wherefore the next-generation TRK-inhibitors are introduced. The diagnosis of NTRK fused tumors, among them sarcomas, remains an issue, as many algorithms but no guidelines exist to date. Given the importance of this diagnosis, in this paper we aim to (1) analyze the histopathological features of sarcomas that correlate more often with NTRK fusions, (2) give an overview of the TRK-inhibitors and the problems that arise from resistance to the therapy, and (3) discuss the diagnostic algorithms of NTRK fused tumors with emphasis on sarcomas.

Larotrectinib in a NTRK-rearranged soft tissue sarcoma in the neoadjuvant setting: A case report

Patients with soft tissue sarcomas should be assessed for neurotrophic tropomyosin receptor kinase (NTRK) gene fusions as neoadjuvant treatment with larotrectinib may prevent amputation.

p53 immunohistochemical analysis of fusion-positive uterine sarcomas

AIMS

Uterine sarcomas can be grouped into tumours with pathognomonic genetic fusions such as low-grade endometrial stromal sarcoma (LGESS), high-grade endometrial stromal sarcoma (HGESS), and inflammatory myofibroblastic tumour (IMT), and tumours lacking genetic fusions such as leiomyosarcoma (LMS) and undifferentiated uterine sarcoma (UUS). Members of the latter group frequently harbour TP53 mutations. The aim of this study was to evaluate TP53 mutations by the use of immunohistochemistry in fusion-positive uterine sarcomas.

METHODS AND RESULTS

We performed p53 immunohistochemical staining on 124 uterine sarcomas harbouring genetic fusions and 38 fusion-negative LMSs and UUSs. These included 41 HGESSs with YWHAE, BCOR and BCORL1 fusions/rearrangements, 13 IMTs with ALK fusion, 12 sarcomas with NTRK1/3 fusion, three sarcomas with PDGFB fusion, and 55 LGESSs with JAZF1, SUZ12 and PHF1 fusions/rearrangements. All HGESSs, LGESSs, IMTs and sarcomas with PDGFB fusion showed wild-type p53 expression. Among NTRK1/3-positive sarcomas, a TPR-NTRK1-positive sarcoma with nuclear pleomorphism showed mutation-type p53 expression. The remaining 11 NTRK1/3-positive sarcomas showed wild-type p53 expression, except for the subclonal p53 mutation-type staining in a minor pleomorphic focus of an NTRK3-positive sarcoma. Twenty-one of 27 (78%) LMSs and six of nine (67%) UUSs showed mutation-type p53 expression.

CONCLUSION

p53 immunohistochemistry may be considered in the initial work-up of a uterine sarcoma, as mutation-type staining would make a fusion-positive sarcoma very unlikely. Mutation-type p53 expression, however, can be seen in a small subset of NTRK1/3-positive sarcomas showing pleomorphic round/ovoid cell histology, which may represent a mechanism of progression in these tumours.

Mesenchymal tumors of the gastrointestinal tract with NTRK rearrangements: a clinicopathological, immunophenotypic, and molecular study of eight cases, emphasizing their distinction from gastrointestinal stromal tumor (GIST)

Mesenchymal tumors driven by NTRK fusions are clinically and morphologically heterogeneous. With an increasing number of clinicopathological entities being associated with NTRK fusions, the diagnostic and predictive value of the identification of NTRK fusions is uncertain. Recently, mesenchymal tumors in the gastrointestinal tract with NTRK fusions were described as gastrointestinal stromal tumors (GIST), but the nosology of such neoplasms remains controversial. We report eight mesenchymal tumors involving the gastrointestinal tract with NTRK1 or NTRK3 rearrangements. The tumors occurred in six children and two adults, five males and three females (age range 2 months-55 years; median 3.5 years), and involved the small intestine (n = 4), stomach (n = 2), rectum (n = 1), and mesentery (n = 1). Clinical outcomes were variable, ranging from relatively indolent (n = 2) to aggressive diseases (n = 2). Morphologically, the tumors were heterogeneous and could be classified in the following three groups: (1) infantile fibrosarcoma involving the gastrointestinal tract (n = 4), enriched for NTRK3 fusions; (2) low-grade CD34-positive, S100 protein-positive spindle-cell tumors, associated with NTRK1 fusions (n = 2); and (3) unclassified high-grade spindle-cell sarcomas, with NTRK1 fusions (n = 2). By immunohistochemistry, the tumors demonstrated diffuse pan-TRK expression, of variable intensity, and lacked a specific line of differentiation. Four cases expressed CD34, which was coexpressed with S100 protein in three cases. Expression of SOX10, KIT, and DOG1 was consistently absent. Molecular genetic testing identified TPM3-NTRK1 (n = 3), TPR-NTRK1, LMNA-NTRK1, and ETV6-NTRK3 (n = 2), and SPECC1L-NTRK3 in-frame gene fusions. We conclude that the evaluation of mesenchymal spindle-cell neoplasms of the gastrointestinal tract without a definitive line of differentiation should include interrogation of NTRK alterations, particularly in pediatric patients. Mesenchymal tumors of the gastrointestinal tract with NTRK rearrangements are clinically and morphologically heterogeneous, and few, if any, seem related to GIST.

Recurrent SPECC1L-NTRK fusions in pediatric sarcoma and brain tumors

The identification of rearrangements driving expression of neurotrophic receptor tyrosine kinase (NTRK) family kinases in tumors has become critically important because of the availability of effective, specific inhibitor drugs. Whole-genome sequencing (WGS) combined with RNA sequencing (RNA-seq) can identify novel and recurrent expressed fusions. Here we describe three SPECC1L–NTRK fusions identified in two pediatric central nervous system cancers and an extracranial solid tumor using WGS and RNA-seq. These fusions arose either through a simple balanced rearrangement or in the context of a complex chromoplexy event. We cloned the SPECC1L–NTRK2 fusion directly from a patient sample and showed that enforced expression of this fusion is sufficient to promote cytokine-independent survival and proliferation. Cells transformed by SPECC1L–NTRK2 expression are sensitive to a TRK inhibitor drug. We report here that SPECC1L–NTRK fusions can arise in a range of pediatric cancers. Although WGS and RNA-seq are not required to detect NTRK fusions, these techniques may be of benefit when NTRK fusions are not suspected on clinical grounds or not identified by other methods.

Recent advances in smooth muscle tumors with PGR and PLAG1 gene fusions and myofibroblastic uterine neoplasms

Uterine epithelioid and myxoid leiomyosarcomas and inflammatory myofibroblastic tumors are rare mesenchymal neoplasms. Next-generation sequencing recently detected novel PGR fusions in uterine epithelioid leiomyosarcomas that demonstrate characteristic rhabdoid and spindled morphology. PLAG1 gene fusions have also been identified in a subset of myxoid leiomyosarcomas and are associated with PLAG1 overexpression. ALK rearrangements underpin the vast majority of uterine inflammatory myofibroblastic tumors, which demonstrate morphologic, and immunohistochemical features similar to those of inflammatory myofibroblastic tumors elsewhere. This review summarizes the morphologic, immunophenotypic, and molecular genetic features of PGR fusion-positive epithelioid leiomyosarcoma, PLAG1 fusion-positive myxoid leiomyosarcoma, and inflammatory myofibroblastic tumors of the uterus.

S100 and Pan-Trk Staining to Report NTRK Fusion-Positive Uterine Sarcoma: Proceedings of the ISGyP Companion Society Session at the 2020 USCAP Annual Meeting

NTRK fusion-positive uterine sarcoma is a recently recognized mesenchymal tumor that is defined by its morphologic resemblance to soft tissue fibrosarcoma, NTRK gene rearrangements, and potential response to Trk inhibition. Reported lesions affect premenopausal women with a median age of 32 yr, and most arise in the uterine cervix. Haphazard, storiform, or herringbone patterns of spindle cells with mild to moderate nuclear atypia are characteristic. SMA, CD34, and S100 are variably positive, but tumors are negative for desmin, ER, PR, and SOX10 and retain H3K27me3 expression. While pan-Trk immunohistochemistry is positive in these tumors, it has decreased sensitivity and specificity in the evaluation of sarcomas in general and the detection of NTRK3 rearrangements. A variety of molecular methods such as fluorescence in situ hybridization and next-generation sequencing may be useful in confirming NTRK fusion in fibrosarcoma-like uterine sarcomas.

Detection of NTRK1/3 Rearrangements in Papillary Thyroid Carcinoma Using Immunohistochemistry, Fluorescent In Situ Hybridization, and Next-Generation Sequencing

NTRK1/3 rearrangements have been reported in 2.3-3.4% of papillary thyroid carcinoma (PTC) and are regarded as potential therapeutic targets. Recently, the application of immunohistochemistry (IHC) to detect NTRK rearrangements has been widely discussed. The current study aimed to characterize the clinicopathological features of PTC with NTRK1/3 fusions, to examine the utility of pan-TRK IHC, and to compare IHC with fluorescent in situ hybridization (FISH) and next-generation sequencing (NGS). In a cohort of 525 consecutive PTC cases, 60 BRAF^V600E-negative cases underwent complete analyses of FISH, and 12 (2.3%) cases with NTRK1/3 break-apart were found. A novel ERC1-NTRK3 fusion was identified by NGS in one case. Pathological features of non-infiltrative tumor border, clear cell change, and reduced nuclear elongation and irregularity were significantly more common in NTRK1/3-rearranged PTC when compared with 48 BRAF^V600E-negative non-NTRK1/3 PTC cases. In whole tissue sections, pan-TRK IHC was positive in 3/7 (42.9%) cases with an ETV6-NTRK3 rearrangement including 2 cases with low percentage of stained tumor cells, 2/3 (66.7%) with non-ETV6 NTRK3 rearrangements, and 2/2 (100%) with NTRK1 rearrangements. All FISH-negative cases were negative for pan-TRK in tissue microarray sections. As a result, pan-TRK IHC showed a sensitivity of 58.3% and specificity of 100% for NTRK1/3 rearrangements in BRAF^V600E-negative PTC. In conclusion, NTRK1/3-rearranged PTC shared some unique morphologic features. Pan-TRK IHC showed high specificity and moderate sensitivity for NTRK1/3-rearranged PTC and should be interpreted with caution due to staining heterogeneity. Based on the above findings, we propose an algorithm integrating morphology, IHC, and molecular testing to detect NTRK1/3 rearrangements in PTC.

Undifferentiated and dedifferentiated neoplasms of the female genital tract

Undifferentiated neoplasms in the female gynecologic tract comprise two main groups-undifferentiated carcinoma, most common in the endometrium and ovary, and undifferentiated uterine sarcoma, although tumors with an undifferentiated appearance may occur in all gynecologic organs. Their differential diagnosis is broad and generous sampling, careful morphological evaluation, judicious use of immunohistochemistry, and in many cases, molecular testing is often essential in the diagnostic work-up. As some of these neoplasms fail to respond to conventional chemotherapy regimens and/or radiation therapy, targeted therapy may be valuable in treating these highly aggressive tumors, thus the importance of precise diagnosis. In this review we discuss the clinicopathological features of undifferentiated carcinoma, dedifferentiated carcinoma, and undifferentiated uterine sarcoma, followed by a comprehensive analysis of morphological mimickers. Finally, we briefly review ovarian and lower genital tract tumors with an undifferentiated histological appearance.