Benign fibroblastic polyps of the colon.

Benign fibroblastic polyps of the colon are a recently described entity among mucosal polyps found in the colorectum. These polyps are typically discovered on routine screening colonoscopy within the distal colon. Benign fibroblastic polyps occur most commonly in adult women in the sixth decade of life. Histologically, benign fibroblastic polyps are bland spindle cell lesions that fill the lamina propria and displace the surrounding crypts. The spindle cell proliferation lacks atypia and significant mitotic activity. Hyperplastic changes are frequently present both in the adjacent epithelium and within the lesions. Immunohistochemically, the cells of benign fibroblastic polyps are invariably positive for vimentin with rare focal positivity for CD34 and smooth muscle actin. They are negative for CD117 and S100 protein. Ultrastructurally, benign fibroblastic polyps have features of fibroblastic differentiation. These polyps are benign with no reports, to our knowledge, of recurrence or metastasis.