A case of malignant granular cell tumor in the sigmoid colon.

Granular cell tumor (GCT) is an uncommon, usually benign neoplasm; however, a malignant potential has been described. Malignant GCT is an extremely rare neoplasm showing rapid growth and invasion into adjacent muscles, lymph nodes, or vessels, or even distant metastasis. We recently experienced a case of a histologically benign or atypical but clinically malignant GCT, with invasion of the lymph nodes and vessels in the sigmoid colon, diagnosed by segmental colon resection with lymph node dissection. We also performed a review of relevant medical literature.