Peritoneal carcinomatosis of unknown primary site may be an undiagnosed appendiceal adenocarcinoma. A case series

BACKGROUND: Peritoneal carcinomatosis is sometimes diagnosed by cytology or by biopsy, but routine radiologic and endoscopic workup may not reveal a primary site. This clinical condition is called adenocarcinoma of unknown primary site. METHODS: The clinical findings of two patients with adenocarcinoma of unknown primary site were presented and the implications for management of similar patients were suggested. RESULTS: The patient had the diagnosis of adenocarcinoma of unknown primary site made when cancer was discovered at the time of umbilical hernia repair or laparoscopy. Radiologic and endoscopic tests were not definitive in providing the primary site for the malignancy. Exploratory laparotomy was performed which revealed an appendiceal mucinous adenocarcinoma as the cause of the peritoneal carcinomatosis. Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) were used at the time of the exploratory laparotomy to treat the appendiceal adenocarcinoma with peritoneal metastases. CONCLUSIONS: Peritoneal carcinomatosis of unknown primary site may be caused by an occult appendiceal adenocarcinoma. This error in diagnosis may lead to suboptimal treatment. Surgical exploration to visualize a normal appendix should occur prior to making a definitive diagnosis of peritoneal carcinomatosis of unknown primary site.