Pan-TRK positive uterine sarcoma in immunohistochemistry without neurotrophic tyrosine receptor kinase gene fusions: A case report.

Background: The classification of uterine sarcomas is based on distinctive morphological and immunophenotypic characteristics, increasingly supported by molecular genetic diagnostics. Data on neurotrophic tyrosine receptor kinase () gene fusion-positive uterine sarcoma, potentially aggressive and morphologically similar to fibrosarcoma, are limited due to its recent recognition. Pan-TRK immunohistochemistry (IHC) analysis serves as an effective screening tool with high sensitivity and specificity for -fusion malignancies.

Case Summary: We report a case of a malignant mesenchymal tumor originating from the uterine cervix, which was pan-TRK IHC-positive but lacked gene fusions, accompanied by a brief literature review. A 55-year-old woman presented to the emergency department with abdominal pain and distension, exhibiting significant ascites and multiple solid pelvic masses. Pelvic examination revealed a tumor encompassing the uterine cervix, extending to the vagina and uterine corpus. A punch biopsy of the cervix indicated NTRK sarcoma with positive immunochemical pan-TRK stain. However, subsequent next generation sequencing revealed no gene fusion, leading to a diagnosis of poorly differentiated, advanced-stage sarcoma.

Conclusion: The clinical significance of gene fusion lies in potential treatment with TRK inhibitors for positive sarcomas. Identifying such rare tumors is crucial due to the potential applicability of tropomyosin receptor kinase inhibitor treatment.