Malignant glomus tumor of the lung.

Primary malignant glomus tumors of the lung are extremely rare, and to our knowledge, only three cases have been described to date. We report one such case in a 53-year-old man who presented with a persistent dry cough. Chest computed tomography scans demonstrated an irregularly shaped mass in the right lower lobe of the lung. Many small nodules were distributed from the main tumor to the periphery, along with bronchovascular bundles. Right lower lobectomy was performed under the diagnosis of lung tumor. The tumor was located in the proximal portion of the right lower lobe and extended along the pulmonary arteries. Histological examination revealed a sheet-like proliferation of epithelioid glomus cells and fascicles of spindle cells. The presence of increased mitotic activity, tumor necrosis and prominent intravascular invasion suggested malignancy. The tumor cells were immunoreactive for vimentin, calponin, h-caldesmon, and alpha-smooth muscle actin, which indicated definitive smooth muscle differentiation. We believe that this is the fourth reported case of malignant glomus tumor of the lung.