The widespread distribution of Langerhans cells in pathologic tissues: an ultrastructural and immunohistochemical study.

Ultrastructural and/or immunohistochemical analysis of approximately 500 specimens revealed widespread distribution of Langerhans cells in pathologic specimens. More than half of the tissue specimens were from patients with a variety of pulmonary diseases. In all specimens in which Langerhans cells were identified ultrastructurally, they were also identified by an immunoperoxidase technique for the visualization of S-100 protein; the latter technique also revealed the dendritic nature of these cells. Langerhans cells were present in 80 to 93 per cent of 66 pulmonary adenocarcinomas and 17 per cent of squamous cell lung cancers; they were not observed in neuroendocrine lung carcinomas or mesotheliomas. They were also observed in benign inflammatory conditions of the lung of several types and in a variety of other malignant neoplasms and disease processes. The Langerhans cells in these tissues varied from few to many. They were most numerous in bronchioloalveolar cell carcinoma, sometimes appearing almost as frequently as tumor cells, and rare in some benign pulmonary conditions and other tumors. The function of Langerhans cells in these conditions is unknown, but they may have an immunologic function, such as antigen processing and presentation to T lymphocytes.