Knowing peritoneal lymphomatosis through PET-TC

Peritoneal lymphomatosis is defined as the intraperitoneal spread of lymphoma. It is a relatively infrequent entity, generally associated with high-grade non-Hodgkin lymphomas. In imaging methods, it is similar to peritoneal carcinomatosis, being generally confused with it if this type of lymphomatosis is not taken into account. Peritoneal lymphomatosis is characterized by diffuse thickening of the peritoneal surface and the greater omentum, with the presence of scattered nodules throughout it, with or without free abdominal fluid, findings that resemble carcinomatosis. Although these entities share some radiologic features, there are some findings that may support the final diagnosis of lymphomatosis, such as multiple enlarged lymph nodes at different levels, larger peritoneal nodules than in carcinomatosis and frequent association with splenomegaly. The evaluation with the greatest yield for staging and monitoring the response to treatment in patients with lymphoma is positron emission tomography-computed tomography (PET-TC) with 18F-fluorodeoxyglucose (18F-FDG). There are two distinct patterns of glucose metabolism on FDG-PET/CT in peritoneal lymphomatosis: a nodular pattern, in which hypermetabolism is related to peritoneal nodules, and a diffuse pattern, with diffuse FDG avidity in peritoneal surfaces and greater omentum. Both patterns are associated with large hypermetabolism lymph nodes. Peritoneal lymphomatosis in general is accompanied by a progressive deterioration in the patient’s clinical condition, therefore the importance of identifying this entity. The purpose of this article is to review peritoneal lymphomatosis and the use of PET-TC for the diagnosis of this entity.