A 70-year-old man was rescued by bloody stool and transient loss of consciousness. Lower gastrointestinal endoscopy showed a type 1 lesion in the ascending colon and a type 2 lesion in the sigmoid colon.
Right hemicolectomy and sigmoid resection were performed for ascending colon and sigmoid colon cancer. The ascending colon was histopathologically a mucinous carcinoma, pT4bN0M0 pStageII.
In the sigmoid colon, squamous cell carcinoma-like tissue and adenocarcinoma-like tissue that were mixed on HE staining, and CK7-positive, CK20-negative, CDX2-negative, CK5/6-positive on immunostaining were diagnosed to be pT3N2M0 pStageIIIB.
Histologically, more than 90% of colorectal malignancies are adenocarcinomas, and adenosquamous carcinomas are reported to account for 0.025% to 0.05% of all colorectal malignancies. In this report, we describe a case of double cancer involving colorectal squamous cell carcinoma and mucinous carcinoma.
