Neuroendocrine differentiation in bronchial carcinomas of classic squamous-cell type - An immunohistochemical study of 29 cases applying the tyramidesignal amplification technique

With regard to the cellular origin of bronchial squamous-cell carcinomas, t here are some clinicopathologic and experimental data indicating a link bet ween neuroendocrine (NE) bronchial tumors and the traditionally non-NE squa mous-cell carcinomas. Against this background, 29 consecutively resected br onchial squamous-cell carcinomas were examined immunohistochemically (IHC) by means of the specific NE cell marker chromogranin A (CgA), using not onl y conventional IHC methods, but also the technique with increased sensitivi ty, offered by the tyramide signal amplification (TSA) procedure. Whereas n one of the 29 tumors displayed CgA immunoreactive (IR) cells using the conv entional IHC procedure, 10 were found to display a fine granular CgA IR in the neoplastic parenchymal cells using the TSA technique. This incidence is higher than previously reported. However, the CgA IR cells never formed an y majority cell population of the neoplastic parenchyma; when present, most of them occurred as micronodules or larger confluent areas in the peripher al most undifferentiated parts of the carcinomatous sheets. Single CgA IR c ells were detected only rarely in the spinocellular or keratinized areas. I t can be speculated that the observations conform with the recently propose d hypothesis that there is a reservoir of NE progenitor cells in the bronch ial mucosa capable of proliferation.