Rare case of appendiceal signet-ring cell carcinoma mimicking advanced ovarian cancer

Primary signet-ring cell carcinoma of the appendix is extremely rare, and because the symptoms are vague and nonspecific, obtaining a preoperative diagnosis is difficult. It cannot be detected using imaging modalities because its radiologic features are undefined, and its appearance on both computed tomography and ultrasound images is similar to that of nontumorous appendicitis. Usually, a diagnosis is made after surgery for other diseases involving the removal of the appendix. The right hemicolectomy is suggested for invasive adenocarcinoma; however, diagnosing primary signet-ring cell carcinoma before surgery and managing tumors with adequate surgical resection remain challenging. We present a case of a large ovarian tumor with peritoneal carcinomatosis diagnosed with advanced ovarian cancer but subsequently revealed through pathology to be primary appendiceal signet-ring carcinoma. Detecting appendiceal signet-ring carcinoma warrants additional surgical management, and treating it involves chemotherapy. This rare disease should be kept in mind when encountering abdominal right lower quadrant pain and tumors to allow for a full treatment plan.