Calcifying Fibrous Tumor in the Rectum

A 41-year-old woman was referred to our hospital because of a rectal tumor detected incidentally by colonoscopy at another hospital. Colonoscopy revealed a submucosal tumor with slightly erythematous surface in the rectum (Figure 1). Endoscopic ultrasonography (EUS) showed a homogeneous hypoechoic lesion measuring 14 mm in diameter with shadowing consistent with calcification. Continuity between the tumor and the muscularis layer was suggested (Figure 2). Due to suspected gastrointestinal stromal tumor (GIST), laparoscopic high anterior resection was peformed. The tumor located in the muscularis layer consisted of spindle-shaped cells with hyalinized fibrocollagenous tissue accompanied by psammomatous calcification and multifocal lymphoplasmacytic infiltrate (Figure 3). Immunohistochemistry showed that the spindle-shaped cells were focally positive for a-SMA (Figure 4), whereas they were negative for CD34, S100, c-kit, and DOG1. The tumor was diagnosed as a calcifying fibrous tumor (CFT).