Two Different Types of Carcinoid Tumors of the Lung: Immunohistochemical and Ultrastructural Investigation and Their Histogenetic Consideration

Abstract

Carcinoid tumors have been an interesting clinical and pathological entity for pathologists because of their unique histopathologic pattern of “Zellballen” (cell ball) and the hormones they produce demonstrable by histochemical and biochemical methods, including immunohistochemistry, and the presence of cytoplasmic dense-core particles demonstrable by electron microscopy. Since carcinoid tumors were established as an entity more than a century ago by Oberndorfer, who was credited with coining the term “carcinoid,” meaning carcinoma-like tumors, tumors presenting with similar characteristics have been reported in most of parenchymal organs, including lungs.Carcinoid tumors in the lungs usually occur as bronchocentric tumors and present with typical histopathologic characteristics of carcinoid tumors, but they may present with significant variation in their cellular compositions, in contrast to the midgut carcinoid tumors. In the latter, tumor cells are quite similar to enterochromaffin granule containing c...