Submucosal Invasive Micropapillary Carcinoma of the Colon with Massive Lymph Node Metastases: A Case Report

Micropapillary carcinoma was originally reported to be an aggressive variant of breast carcinoma, and it is associated with frequent lymphovascular invasion and a dismal clinical outcome. It has subsequently been found in other organs; however, at present, only a limited number of cases of colorectal micropapillary carcinoma have been reported. We present a case of early colon cancer with extensive nodal metastases in a Japanese patient. An 82-year-old man was found by colonoscopy to have a 20-mm pedunculated polyp in his sigmoid colon. Endoscopic resection of the sigmoid colon tumor was performed, and pathological examination of the resected specimen revealed a poorly differentiated adenocarcinoma component and a micropapillary component. Despite the tumor being confined within the submucosa, massive lymphatic invasion was noted. Thereafter, the patient underwent laparoscopic sigmoidectomy with lymph node dissection, and multiple lymph node metastases were observed. Our case suggests that when a micropapillary component is identified in a pre-operative biopsy specimen, even for early colorectal cancer, surgical resection with adequate lymph node dissection would be required because of the high potential for nodal metastases.