Utility of histopathological revision in the management of gastro-entero-pancreatic neuroendocrine neoplasia

Background: Histological evaluation and grading assessment are key points in the diagnostic work-up of gastroentero-pancreatic neuroendocrine neoplasms (GEP-NENs). Aim: To analyze the impact of histopathological revision on the clinical management of patients with GEP-NEN. Materials and methods: Patients referred to our Center of Excellence between 2015 and 2021 were included in this study. Immunohistochemical slides at the time of initial diagnosis were reviewed to assess tumor morphology, diagnostic immunohistochemistry, and Ki67. Results: 101 patients were evaluated, with 65 (64.4%) gastrointestinal, 25 (24.7%) pancreatic, and 11 (10.9%) occult neoplastic lesions suspected to be of GEP origin. The main changes resulting from the revision were: first Ki-67 assessment in 15.8% of patients, Ki-67 change in 59.2% of patients and grading modification in 23.5% of patients. An additional immunohistochemical evaluation was performed in 78 (77.2%) patients, leading to a confirmation of GEP origin in 10 of 11 (90.9%) of unknown primary site neoplastic lesions and an exclusion of NEN diagnosis in 2 (2%) patients. After histopathological revision, a significant modification in clinical management was proposed in 42 (41.6%) patients. Conclusions: Histopathological revision in a referral NEN center is strongly advised in newly diagnosed GEP-NENs to properly plan prognostic stratification and therapeutic choice.