Neuroendocrine neoplasms of lung, pancreas and gut: a morphology-based comparison

The bronchopulmonary (BP) and gastroenteropancreatic (GEP) organ systems harbor the majority of the neuroendocrine neoplasms (NENs) of the body, comprising 20 and 70% of all NENs, respectively. Common to both NEN groups is a classification distinguishing between well- and poorly differentiated NENs associated with distinct genetic profiles. Differences between the two groups concern the reciprocal prevalence of well and poorly differentiated neoplasms, the application of a Ki67-based grading, the variety of histological patterns, the diversity of hormone expression and associated syndromes, the variable involvement in hereditary tumor syndromes, and the peculiarities of genetic changes. This review focuses on a detailed comparison of BP-NENs with GEP-NENs with the aim of highlighting and discussing the most obvious differences. Despite obvious differences, the principle therapeutical options are still the same for both NEN groups, but with further progress in genetics, more targeted therapy strategies can be expected in future.