A Case of Malignant Granular Cell Tumor in the Sigmoid Colon
A 43-year-old female patient visited SAM Medical Center for further evaluation of a submucosal tumor that was seen on prior colonoscopy in another clinic. She was asymptomatic, and a physical examination showed unremarkable findings. The laboratory results showed a white blood cell count of 4,100/mm2, hemoglobin of 7.7 g/dL, platelet count of 340,000/mm2, albumin of 4.4 g/dL, aspartate aminotransferase of 13 IU/L, and alanine aminotransferase of 7I IU/L. Colonoscopy showed a yellowish, round submucosal tumor with intact mucosa, approximately 1 cm in diameter in the sigmoid colon (). Endoscopic ultrasonography (EUS) revealed an approximately 1×1 cm hypoechoic heterogeneous mass with a smooth margin originating from the third echo layer (). Because the diagnosis was benign GCT or carcinoid tumor, and the tumor was relatively small, we decided to follow the patient after 1 year, after she was given sufficient explanation about the malignant potential of the lesion. At the follow-up colonoscopy 1 year later, the size of the tumor increased to approximately 3 cm. We performed segmental colon resection with lymph node dissection, and the pathologic gross finding showed the tumor to be well circumscribed and located at the submucosal and muscular layers with central infiltration of the serosa. Histologic examination revealed proliferation of large polygonal cells with abundant eosinophilic granular cytoplasm, which was positive for S-100 and invasion of local lymph nodes and vessels (). Two of the histologically malignant criteria of GCT-presence of vesicular nuclei with large nucleoli and pleomorphism-were met, and the tumor was diagnosed as a histologically benign or atypical but clinically malignant GCT occurring in the sigmoid colon.