Synchronous Neuroendocrine Tumor and Mucinous Tumor of the Appendix in a 76-Year-Old Woman

A 76-year-old woman presented with a one-year history of intermittent right lower abdominal pain, little weight loss, and palpable mass in the right lower quadrant of the abdomen. Pelvic ultrasound scan identified a lobulated hypo-hetero-echoic mass with some calcified foci. Computed tomography scan revealed a low-attenuated lesion-like mass in the perineal region, which suggested a cystic localized tumor. Colonoscopy showed sub-mucosal lesion in the cecum. The patient underwent laparotomy, and a right hemicolectomy (include ileum) with ileocolic anastomosis was performed. She was treated successfully. In the Histological examination, two mass-like lesions were found to attach to the appendix. In the proximal portion of the appendix, there were cystic structures that showed a low-grade appendiceal mucinous neoplasm. The tip of the appendix showed a well-differentiated neuroendocrine tumor (carcinoid tumor). In this unusual case, even though the initial origins of these two tumors are quite different, two tumors appeared in a single histological section.