Benign clear cell tumor of the lung. An Ultrastructural Study

The ultrastructural features of a benign clear cell tumor of the lung are reported. The tumor cells showed monogranular, rosette, and membrane‐bound glycogen which appears unique to this tumor. Many tumor cells were surrounded by basement membrane material, and were in close association with endothelial cells. The cytoplasmic membrane of the cells showed electron‐dense deposits alternating with pinocytotic vesicles. Many cells showed intracytoplasmic filaments. The ultrastructural features suggest a smooth muscle or pericytic origin for this neoplasm.