The aspiration cytology of pulmonary hamartomas.

Cytodiagnosis of pulmonary hamartomas (PHs) by transthoracic fine-needle aspiration (FNA), successful in 11 of a series of 14 cases, has been found to rely less on the presence of mature cartilage than on the recognition of fibromyxoid fragments. These fragments, wispy yet discrete, consisting of variable numbers of fibroblasts embedded in fibrillary ground substance, can be distinguished from fibrous tissue and mucus, both of which they may resemble. Mature cartilage is distinctive when present, but it is seen in a minority of cases. Bronchial cells and adipocytes, integral components of PHs, are of no diagnostic value unless associated with fibromyxomatous tissue or cartilage. Chest wall "contaminants" that may cause pitfalls in diagnosis, such as bone, skeletal muscle, and fibrous tissue, are described and illustrated. The differential diagnosis of biphasic lesions containing epithelial cells and mesenchyme, including dermoids and blastomas, is discussed. With knowledge of the radiologic appearance of target lesions, confident cytodiagnosis of PHs is possible if attention is paid to subtle, yet specific, background features in aspirated material.