Malignant transformation of primary mature teratoma of colon: A case report

Mature teratoma is a common benign ovarian germ cell tumor, accounting for about 20% of ovarian tumors. The malignant transformation of this tumor is less than 2%. The most common type is squamous cell carcinoma, followed by adenocarcinoma. Malignant transformation of colonic mature teratoma is extremely rare. We here report a case of malignant transformation of primary mature teratoma of the colon. The type of malignant transformation was adenocarcinoma.

A 63-year-old woman was admitted to our hospital due to persistent pain in her right lower abdomen for 1 mo, and she had no nausea, vomiting, blood in the stools, or other symptoms. Preoperative colonoscopy showed uplift of the sigmoid colon mucosa and submucosa. The biopsy showed squamous epithelium. However, contrast-enhanced computed tomography of abdomen and pelvis showed a localized thickening of the sigmoid wall, suggesting colon cancer. Endoscopic ultrasonography (EUS) revealed that the structure of the intestinal wall at the base of the lesion was destroyed, and the boundary between the lesion and the surroundings was unclear. According to the findings of the EUS, the patient did not undergo endoscopic submucosal dissection, but underwent radical resection of the tumor. Histologically, squamous epithelium was seen on the mucosal surface of the colon wall, cartilage and glands were seen under the epithelium, and adenocarcinoma was seen on the muscular layer and serous surface. The final pathological diagnosis was malignant teratoma of the colon. We have followed up the patient for 2 mo since the operation, and the patient recovered well.

This case suggests the possibility of mature teratoma in the colon and recognition of malignant types, and it should not be considered as an exclusively ovarian tumor.