Large clear cell tumor of the lung mimicking malignant behavior.

An 18-year-old man presented with a large (12 x 10 cm) cystic mass involving the lower lobe and lingula of the left lung on computed tomography. Intraoperatively a large cystic mass was seen densely adherent to the left lung and the chest wall. A left pneumonectomy was performed because of the dense adhesions and extreme vascularity. Pathologic examination revealed a benign sugar cell tumor of the lung. We believe this is the first case report of such a large, clear cell tumor of the lung, mimicking malignant behavior in terms of vascularity and local invasion and requiring pneumonectomy.