Malignant behavior of a well‑differentiated digestive neuroendocrine tumor with peritoneal carcinomatosis: A case report.

Neuroendocrine neoplasms (NENs) are a heterogenous group of tumors, arising from enterochromaffin cells, with different biological and clinical characteristics. Well-differentiated Grade 1 (G1) small intestinal NENs are often characterized by a slow progression rate and a good prognosis. Peritoneal carcinomatosis of a G1 digestive NEN is not a very common finding, and thus there is little published evidence regarding its progression and management. The complex, multistage interplay between the peritoneum and the metastasizing neuroendocrine cells is not well understood, and a reliable predictive tool to identify these patients earlier in their disease course is lacking. The present study describes the case of a 68-year-old woman presenting with an oligosymptomatic, stage IV, small intestinal G1 NEN (pTxpN1pM1) with synchronous liver metastases, multifocal mesenteric tumor deposits and a low Ki67 labeling index (1%). Over a period of 15 months, the patient developed rapidly progressive peritoneal metastatic disease with repetitive self-limiting obstructive symptoms and eventually succumbed to her illness. The present case report discusses the potential relationship between low-grade NEN, location of the primary tumor and the metastatic site, and also speculates on the role of the underlying subcellular mechanisms, specific micro-environment, spreading modalities and therapeutic strategy.