Intravascular bronchioloalveolar tumor (IV-BAT).

Intravascular bronchioloalveolar tumor (IV-BAT) is a recently described, histologically distinct, malignant, primary lung neoplasm. Originally it was believed to arise from type II alveolar cells which invade blood vessels within the lung, and hence its name. More recent ultrastructural studies suggest an origin from mesenchymal cells, and therefore the tumor may be more appropriately considered a sarcoma. The onset of the disease may be insidious, and its clinical course may vary from slow to rapid progression. A history is present of a young woman with slowly enlarging multiple ill defined pulmonary nodules. Open lung biopsy was diagnostic of IV-BAT. The clinical course, differential diagnosis and pathogenesis of this tumor are briefly discussed.