Undifferentiated spindle cell sarcoma at the anastomosis after ileocecal resection for colon cancer: A case report

Spindle cell sarcoma (SCS) is a sarcoma subtype rarely described in the abdominal cavity, and with a worse prognosis compared with that at other sites. We report a case of SCS occurring at the anastomosis after ileal resection for colorectal cancer.

An 86-year-old woman with a chief complaint of abdominal pain had undergone ileal resection, D2 dissection, and hand-sewn anastomosis in 2011 to treat papillary stage I adenocarcinoma. In February 2023, the patient was referred to our hospital because of progressive anemia, and a full circumferential type 3 tumor was found at the anastomosis site after resection of the ascending colon. Biopsy revealed a malignant spindle tumor. The patient underwent an open right hemicolectomy of the colon and limited lymph node dissection. The final pathological examination revealed an undifferentiated SCS centered on the anastomosis. Postoperative follow-up imaging is ongoing, and there has been no recurrence.

SCSs are a group of tumors composed of spindle-shaped cells. Diagnosis based solely on morphology is difficult. The final diagnosis was based on the results of immunostaining and genetic testing. A diagnosis of sarcomatous transformation due to local recurrence was ruled out. Since the possibility of a dedifferentiated liposarcoma remained, a definitive diagnosis of undifferentiated SCS with an undetermined differentiation direction was not confirmed.

SCS is a rare disease, and this is the first reported case of SCS occurring in the colon or during colonic anastomosis. Additional cases are necessary to determine an appropriate treatment strategy.