Diagnosis of pulmonary hamartoma by fine needle biopsy

OBJECTIVE: To review the features of pulmonary hamartoma (PH) on fine needle biopsy (FNB), with emphasis on features that allow specific diagnosis. STUDY DESIGN: Fourteen cases of PH diagnosed on FNB were reviewed. The presence and volume of aspirate components were recorded. Attention was paid to features that might lead to false positive diagnosis of malignancy. Immunohistochemical staining for S100 was performed on cell block material. RESULTS: Fibromyxoid stroma and chondroid material were seen in 93% and 79% of cases, respectively; 71% demonstrated both components. Fibromyxoid stroma was prominent in the majority of cases; chondroid material was less abundant, being scanty in over half of cases. There were no cases in which epithelial cells represented the sole prominent component, and significant epithelial atypia was not identified. S100 staining was demonstrable in all cases in which stromal material was present in the cell block. CONCLUSION: A correct specific diagnosis of pH requires identification and correct interpretation of either fibromyxoid stroma or cartilaginous material. These components may show variable appearance on smears, with a range of potential mimics and pitfalls, but specific features are recognizable. Immunohistochemical staining of stromal material with S100 may lend support to the diagnosis.