Abstract
Mucinous neoplasms of the appendix, including low-grade appendiceal mucinous neoplasms (LAMNs), are rare but significant due to their potential for peritoneal dissemination. These tumors are often discovered incidentally during imaging or surgery for unrelated conditions. The presence of mucinous material in the peritoneum raises concern for pseudomyxoma peritonei, necessitating careful intraoperative and postoperative management. A 52-year-old male presented with testicular pain, leading to a diagnosis of seminoma. Staging computerized tomography (CT) revealed a dilated appendix with a surrounding fluid collection, suggestive of a ruptured mucocele. Exploratory laparotomy uncovered a large mucinous mass encasing the appendix, with mucinous deposits in the peritoneum. Final pathology confirmed an invasive mucinous adenocarcinoma, well-differentiated, arising in the background of a low-grade mucinous appendiceal neoplasm. The invasive component extended into the subserosa (pT3), while the LAMN component involved the serosa (pT4a). When mucin is found intraoperatively, surgeons should consider appendectomy with possible conversion to an open approach for thorough exploration. Emergency HIPEC is unnecessary; instead, it should be planned electively after complete cytoreduction. The prognosis depends on the extent of the disease and the success of cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC).