Clear cell sarcoma (CCS), is an uncommon malignant soft tissue neoplasm that displays melanocytic differentiation with a distinct molecular profile. It is very rarely localized in gastrointestinal tract. We reported the first case of a primary CCS arising in pancreas. A 36-year-old man presented with jaundice for one month. A preoperative abdominal computer tomography showed a low-density mass in the head of pancreas. Whipple procedure was performed and the tumor was resected. Pathological examination showed polygonal or fusiform cells arranged in a uniform nested to fascicular growth pattern with thin fibrous septa. Immunohistochemical studies revealed positivity for HMB-45, Melan A, S-100, MiTF and vimentin protein. Fluorescence in situ hybridization on paraffin section showed a translocation involving the EWSR1 gene region. No BRAF and NRAS mutation was detected. The patient underwent transcatheter arterial chemoembolization (TACE) six times and eventually died of diffuse liver metastasis 10 months later. This case illustrates that the pancreas is a potential site for primary clear cell sarcoma and molecular studies play an important role in making a conclusive diagnosis.
Keywords: Clear cell sarcoma; EWSR1; FISH; immunohistochemistry; pancreas; translocation.