Alveolar soft part sarcoma occurs mostly in the deep soft tissues. An unusual case of primary pulmonary alveolar soft part sarcoma is reported. A 39-year-old woman presented with thoracic pain revealing the tumor. The left lower lobe was surgically resected. The microscopic features of this tumor, including characteristic alveolar pattern and the PAS-positive crystals were typical of alveolar soft part sarcoma. Immunohistochemically, granular cytoplasmic reactivities were observed with antibodies against vimentin, myoglobin, methionine-enkephalin, S100 protein and neuron-specific-enolase. Electron microscopic study demonstrated numerous crystallized structures in the tumor cell cytoplasm. This is the third case of pulmonary alveolar soft part sarcoma, one arising from the pulmonary vein. The histogenesis of alveolar soft part sarcoma is still debated. Our case does not allow distinction between myogenic or neural origin of this tumor.