[Immunocytochemical studies in the diagnosis of pulmonary histiocytosis X]

The diagnostic value of immunocytochemical tests was analysed for 19 cases of pulmonary histiocytosis X (PHX) and eight of other types of fibrosing pulmonary disease (sarcoidosis, 3; exogenous allergic alveolitis, 3; chronic pneumonia, 1; fibrosing alveolitis, 1). The cellular, proliferative-fibroblastic and fibrocystic stages in the course of pulmonary changes were differentiated. PHX cells reacted with anti-S 100 protein in all stages. In three cases for which unfixed tissue was available, all PHX cells reacted with antibody Leu-6, and 35% of these cells also reacted with the proliferation marker Ki-67. The few S-100 positive cells from the eight controls were limited to peribronchial tissue. Thus the antibodies Leu-6 and S-100 are useful aids in the diagnosis of PHX.