Objective: To report about a primary leiomyoma of the lung, with clear cell features and with admixed alveolar epithelium.
Results and conclusions: The patient, a 18-year-old female, non smoker, presented with a well-delimited pleuro-pulmonary mass, 6,5 cm across, located in the right upper lobe. The mass was discovered 5 years previously, following an episode of spontaneous pneumothorax; initially interpreted as an intralobar pulmonary sequestration, it was subsequently removed due to a small dimensional increase. A gynaecological examination, a thoracic CT-scan obtained 2 years after operation, and a recent abdomino-pelvic echography were negative. The patient is alive and well 7 years after surgery. Microscopically, the lesion was well delimited and it was punctuated by multiple cysts of variable dimensions, covered by bland cubic cells. The solid part of the lesion was composed by oval, clear cells, merging with fusiform elements with densely eosinophilic cytoplasm. Significant atypia, mitoses and necrosis were absent. Immunohistochemically, both oval and spindle cells were strongly positive for vimentin, smooth muscle actin, desmin and h-caldesmon, negative for cytokeratin, EMA, CD-34, CD-10, CD-117, HMB-45, TTF-1, BCL-2, GFAP, calretinin, chromogranin, estrogen and progesterone receptors. Cells covering the cystic spaces were positive for cytokeratin, TTF-1 and EMA, negative for all the other antibodies tested. Smooth muscle proliferations of the lung are briefly discussed, together with the most important problems in differential diagnosis.