Chapter 31 - Neuroendocrine tumors and other neuroendocrine proliferations of the lung

Summary

Introduction

Cells with the neuroendocrine phenotype synthesize and secrete amine or peptide hormones that regulate local physiological processes. They act in concert with systemic neural and endocrine control systems. These cells have features of both neurons and of endocrine cells, hence their name. Whether scattered as individual cells within epithelia, as in the airways or gut, or aggregated into larger structures, such as the pancreatic islets, neuroendocrine cells are characterized by their morphological uniformity and high degree of organization; that is to say, they “look” neuroendocrine. Their ultrastructural hallmark is the neurosecretory or dense core vesicles (DCVs) that store and release their secretory products (see Chapter 1). Components of these and other secretory vesicles, together with a variety of membrane proteins and enzymes, endow neuroendocrine cells with a characteristic antigenic profile. These unique features are recapitulated in the neoplasms that differentiate along neuroendocrine lines. With this particular phenotype, morphological, functional and antigenic characteristics allow such tumors to be recognized as neuroendocrine.

It is not surprising the lungs give rise to tumors characterized by neuroendocrine differentiation, since a widely dispersed and dynamic population of peptide and amine-secreting pulmonary neuroendocrine cells (PNCs) is an integral part of the respiratory epithelium (see Chapter 1). Why neuroendocrine differentiation is so common amongst pulmonary tumors is an unanswered question. The prevalence of such neoplasms in the lungs contrasts markedly with that in other epithelia, such as those lining the gastrointestinal, urinary and reproductive tracts, where neuroendocrine cells are also found, but the corresponding tumors are rare.