A rare case of synchronous adenocarcinoma and ancient schwannoma in the colon

초록

Gastrointestinal schwannomas are uncommon benign mesenchymal neoplasms that can mimic adenocarcinoma and colon schwannomas are extremely rare. A 66-year-old male with past history of pancreatic surgery carried out colonoscopy for routine health examination. A colonoscopy revealed a 1.5 cm sessile polyp in the upper rectum and another 3.0 cm well defined cylindrical mass with central ulceration in the descending colon. The rectal mass was removed by snare polypectomy during a colonoscopy and confirmed on pathology to be an intramucosal adenocarcinoma with positive deep margins. The colonoscopic biopsy, on the other hand, failed to prove a nature of the descending colon mass. The patient was referred to surgery for segmental resection of the descending colon and low anterior resection for resection of rectal adenocarcinoma. The mucosal surface of the descending colon showed a 2.7 x 2.5 cm grayish yellow fungating mass, extending to the pericolic adipose tissue. Pathological examination of the resected rectum revealed brownish irregular ulcerative mucosal erosion, measuring 1.5 x 1.0 cm at the site of previous polypectomy with no residual cancer cells. Immunohistochemistry revealed the descending colon mass to be positive for S100 protein, but negative for CD34, CD117(C-kit), smooth muscle actin and desmin, with a Ki-67 proliferative index of less than 2%. These histopathological findings showed features compatible with an ancient schwannoma. The patient was discharged from the hospital without complications on the 8th postoperative day. We present a rare case of coexistent descending colon ancient schwannoma with synchronous primary rectal adenocarcinoma.