Cytologic and histologic findings in a case of tracheobronchial papillomatosis.

tracheobronchial papillomatosis is a rare pathologic entity that should be considered in the differential diagnosis of bronchogenic squamous cell carcinoma. Although well differentiated histologically, papillomatosis has an aggressive pattern of growth, producing multiple and extensive endobronchial lesions that grossly simulate advanced malignancy. Cytologic examination shows atypical but not anaplastic features. These include unique, regular-layered arrangements of keratin resembling keratotic plugs, which may be specific for this tumor. Malignant transformation has been reported.