Histochemical studies of dense-core granulated tumors of the lung. Neuron-specific enolase as a marker for granulated cells

It is well known that carcinoid tumors and some small-cell carcinomas of the lung contain dense-core granules (DCGs). Moreover, a small number of tumors presenting with epidermoid, large-cell, or adenocarcinoma histologic characteristics (so-called atypical endocrine tumors), also contain DCGs. Herein, we describe certain histochemical features of DCG tumors and compare them with other major lung tumor types that lack DCGs (non-DCG tumors). All DCG tumors contained neuron-specific enolase and many contained serotonin. These markers were not present in any non-DCG tumor. Other histochemical markers (glycogen, mucosubstances, corticotropin, β-human chorionic gonadotropin, keratin, somatostatin, and calcitonin) were found in a proportion of DCG and non-DCG tumors, but were, in general, more common in non-DCG tumors and atypical endocrine tumors than in carcinoids and small-cell carcinomas. α-Fetoprotein was rarely found in non-DCG tumors, and was never observed in DCG tumors. The atypical endocrine group represents a class of tumors with a remarkably mixed and varied phenotype. Their potential significance is discussed and methods to facilitate their diagnosis are suggested.