Synovial Sarcoma of the Descending Colon: Report of a Rare Case and Review of the Literature

Abstract

Abstract Introduction/Objective Synovial Sarcoma is a mesenchymal malignancy that occurs primarily in the deep soft tissue near large joints of the extremities in young adults. Synovial sarcoma of the gastrointestinal tract is extremely rare. There is not enough literature to establish a consensus on management and treatment for colorectal synovial sarcoma. Methods/Case Report An 85-year-old male preresented with a positive cologuard test and the colonoscopy revealed a 12 mm polyp in the descending colon. Polypectomy was preformed. Histological examination exhibits spindle cell proliferation with fascicular growth pattern and with small nucleoli. There are collagen deposition, variable size of thick wall vessels and mixed inflammatory cells including lymphocytes, eosinophils and neutrophils in the background. Mitosis are identified. Immunohistochemical stains show tumor cells are negative for CD34, S100, DOG1, CD117, STAT6, Bcl-2, Desmin, and AE1/AE3, and focal positive for EMA, SMA and ALK. Immunohistochemical stain for SS18-SSX fusion protein is positive. Archer fusionplex targeted RNA sequencing (M23-1377) showed SS18:SSX2 fusion. A structural genomic alteration between the SS18 and SSX2 genes is detected [t(18;X)(q12.1;p11.22)]. These findings confirmed the diagnosis of synovial sarcoma. Results (if a Case Study enter NA) NA Conclusion Here we report a rare case of descending colon primary synovial sarcoma. Synovial sarcoma is generally considered as an aggressive and high-grade lesion with metastatic potential and its management is different from other colorectal neoplasms. This case report emphasies a wide differential diagnosis for colorectal lesions and prompt diagnosis and early management is important for better patient outcome.