HighlightsThere are only two cases reported in the literature Merkel cell carcinoma in the retroperitoneum.The most plausible theory is the retroperitoneal mass could be a massively enlarged lymph node where precursor cells became neoplastic.The less probable theory is the non-described “regression” phenomena of a cutaneous MCC, but we are not found a primary skin lesion.Preoperative chemotherapy and excision of the primary tumor is the surgical treatment of choice for retroperitoneal MCC.

Patients with peritoneal carcinomatosis (PC) of gastric origin have a poor prognosis of life with an average survival of 1-3 months. Systemic chemotherapy has improved the survival of those patients with gastric metastatic cancer at 7-10 months. However, this benefit could not be reproduced in those patients with PC. The current literature for the use of hyperthermic intraperitoneal chemotherapy (HIPEC) for gastric PC has significant variation related to patient selection, treatment intent (palliative vs. attempt at curative treatment), surgical technique, intraperitoneal chemotherapy agent utilized, and systemic chemotherapy administered adjuvantly. From the perspective of patient selection for cytoreduction and HIPEC, patients with extensive PC are not candidates. In addition, unresectable location would make a patient a poor candidate for cytoreduction and HIPEC. Optimally, those with positive peritoneal cytology alone could benefit most. However, the role of cytoreductive surgery and HIPEC in patients with PC of gastric origin has not yet been clarified.