Histopathological Revision for Gastro-Entero-Pancreatic Neuroendocrine Neoplasms in Expert Centers: Does it Make the Difference?

Histopathological Revision for Gastro-Entero-Pancreatic Neuroendocrine Neoplasms
in Expert Centers: Does it Make the Difference?: Background: The histopathological correct diagnosis of gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs) is crucial for treatment selection and prognostication. It is also very challenging due to a limited experience in non-expert centers. Revision of pathology is standard of care for most patients who are referred to NEN expert centers. Objectives: To describe the clinical impact of histopathological revision for GEP-NEN patients referred to an expert center. Methods: Retrospective multicenter analysis of all GEP-NENs receiving a histopathological revision in 6 European NEN expert centers (Jan 2016‒Dec 2016) to evaluate the impact on patient management Results: 175 patients were included and 14.7% referred for a second opinion. Histological samples were 69.1% biopsies, 23.4% surgical specimens and 7.5% endoscopic resections. Histopathological changes due to revision included: first assessment of Ki67 in 8.6% of cases, change in grading in 11.4% (3.4% G1 to G2; 5.7% G2 to G1; 0.6% G2 to G3; 1.7% G3 to G2), definition of tumor invasion in 10.8%, additional immunohistochemical staining in 2.3%, diagnosis of mixed adeno-neuroendocrine carcinoma (MANEC) in 3.4%, exclusion of a NEN in 3.4%, first diagnosis of NEN in 2.3%, tumor differentiation for G3 in 1.7%. The revision had a clinical impact in 36.0% of patients, leading to a new therapeutic indication in 26.3%. Indication to then perform a new imaging test occurred in 21.1%, and recommendation to follow-up with no further treatments in 6.3%. Conclusions: Histopathological revision in expert centers for NENs can change the diagnosis, with a significant clinical impact in about one third of patients.