Pulmonary cysts as the sole metastatic manifestation of soft tissue sarcoma: case report and consideration of the pathogenesis.

A 29-year-old woman with an unusual form of pulmonary metastasis from epithelioid sarcoma of the right forearm is presented. Since she manifested left pneumothorax due to metastatic pulmonary cyst 7 years ago, the only metastatic manifestation has been the presence of bilateral multiple thin-walled pulmonary cysts; no other types of pulmonary lesions, such as nodules, cavitary lesions with thick or irregular walls, or extrapulmonary metastases, have been found. Pathologic studies revealed metastatic proliferation of sarcoma cells in the wall of the pulmonary cysts and infiltration of malignant cells inside the microscopic cavitary metastases surrounded by normal lung parenchyma.