Abstract
We report here a case of a benign fibroblastic polyp (BFP) of the sigmoid colon. Colonoscopy was performed for a 65-year-old man for the purpose of screening for colorectal cancer. Screening revealed a small (5 mm) protruding polyp that appeared like a submucosal tumor at the sigmoid colon, and endoscopic mucosal resection was performed. In hematoxylin and eosin stained sections there was a proliferation of monomorphic benign-appearing spindle cells in the lamina propria. Immunohistochemical staining revealed strong positivity for vimentin in the spindle cells. With the exception of focal positivity for CD34, staining for epithelial membrane antigen, alpha-smooth muscle actin, desmin, S-100, c-Kit and PDGF was negative. Ki-67 labeling demonstrated low positivity. These features were consistent with the diagnosis of BFP. BFP is a recently described entity and its true nature or etiology is still unknown. The differential diagnosis of BFP includes the presence of other spindle cell proliferations in the gastrointestinal tract, which may have features of mucosal polyps or submucosal tumors, including smooth muscle tumors, gastrointestinal stromal tumors, neurofibroma, schwannoma, intestinal perineurioma, and inflammatory fibroid polyps. This is the first case report of BFP in Japan.
