Fig. 3
Immunophenotypical characterization of OPA. a The neoplastic epithelial cells of classical form are diffusely and intensely immunopositive for MCK; b TTF1-positive nuclei of the epithelial cells are present within the neoplastic masses. Inset: the bronchial epithelium was used as positive control for TTF1. c All epithelial cells lining neoplastic acini are negative for vimentin (blue arrow) in contrast to immunopositive stromal cells (white arrow); d Myxoid growths showing an intense immunopositive reaction for Vimentin. Inset: detail of diffuse cytoplasmic labeling for Vimentin; e Mesenchymal cells of myxoid growths have diffuse and strong cytoplasmic labeling for Desmin. Inset: The smooth muscle cells of pulmonary arteries and bronchioles are strongly positive for desmin and served as internal positive control; f The cells of myxoid growths have selective and moderate cytoplasmic labeling for alpha-SMA. Inset: The bronchiolar smooth muscle cells are positive for SMA, internal positive control; g The myxoid component of OPA showing a negative immunoreaction of MCK (blue arrow) compared to the neoplastic epithelial cells which are strongly immunopositive; h Neoplastic cells of myxoma-like nodules showing a negative reaction for S100 protein. Inset: the bronchial cartilage is diffusely positive for S100 protein, internal positive control; i The proliferative index, characterized by ki67 immunopositive nuclei, was higher in the epithelial neoplasia compared to the MGs and myxoma-like nodules (blue arrows) (j). Inset: Bronchial-associated lymphoid tissue (BALT) hyperplasia was used as internal positive control for ki67. DAB and hematoxylin counterstain