Pseudo-peritoneal carcinomatosis: extensive endosalpingiosis mimicking metastatic dissemination in gastric cancer : a case report and literature review

We report an exceptional diagnostic pitfall in which extensive benign endosalpingiosis mimicked stage IV peritoneal carcinomatosis in a patient with gastric cancer, emphasizing the critical role of histopathological confirmation in staging. A 57-year-old female was diagnosed with poorly differentiated gastric adenocarcinoma. Initial staging imaging revealed diffuse peritoneal nodules suggestive of carcinomatosis. The patient received perioperative chemotherapy followed by reassessment, with persistent peritoneal lesions, prompting diagnostic laparoscopy with biopsy. Intraoperative findings showed diffuse millimetric peritoneal nodules indistinguishable from metastatic disease. Frozen section and final histopathology demonstrated florid endosalpingiosis without malignancy. Despite a radiological stage IV suspicion, the patient was ultimately confirmed as non-metastatic (M0) and underwent curative-intent total gastrectomy with D2 lymphadenectomy, achieving an R0 resection. Extensive peritoneal endosalpingiosis may closely mimic peritoneal carcinomatosis in gastric cancer. This case highlights the essential role of systematic histological confirmation in preventing incorrect stage IV classification and inappropriate therapeutic management strategies.