Pulmonary Tumorlet with Foci of Neuroendocrine Cell Hyperplasia in the Bronchus: A Case Report
Herein reported is a case of pulmonary tumorlet with foci of neuroendocrine cell hyperplasia in a bronchus and bronchiole which was found in a 84-year-old man without chronic pulmonary disease. Histologically, aggregates of neuroendocrine cells were situated in peribronchial fibrotic parenchyma and had been multifocally scattered in a disparsed fashion to form a minute nodule. The lesion exceeded a little over 0.5 cm in size at greatest dimension, and was diagnosed as pulmonary tumorlet of oat cell type. In addition, minute aggregates of neuroendocrine cell hyperplasia were present in bronchial and bronchiolar epithelium and represented hyperplasia. Immunohistochemical staining for chromogranin A, synaptophysin, GRP and serotonin comfirmed that these cells were in fact neuroendocrine cells, showing a strong positivity for GRP, chromogranin A, synaptophysin and a weak positivity for serotonin. The tumor cells were negative for p53, and Ki-67 labeling indices (LI) were less than 0.5 in both lesions, indicating that these cells were not actively proliferating in the manner of a malignant neoplasm. Our results suggest that these lesions may well be hyperplastic rather than neoplastic. The nature of the pulmonary tumorlet and its histogenesis is discussed.