Benign and Malignant Mesenchymal Tumors of the Lung

Mesenchymal tumors of the lung are rare neoplasms that may range from benign, incidental lesions to highly aggressive sarcomas. Given that the lung is the most common site of spread for soft tissue sarcomas, pulmonary mesenchymal tumors are most often the result of metastatic spread from primary lesions at other sites rather than representing primary tumors arising from the lung parenchyma. However, primary lung mesenchymal neoplasms do occur and include nearly all histogenetic categories. This includes tumors of various different subtypes including fibroblastic, smooth muscle, adipocytic, neurologic, vascular, bone, cartilage, and undifferentiated tumors. Malignant mesenchymal tumors are more common in the lung than benign ones and often present with an aggressive clinical course. Both the benign and malignant lesions that occur as lung primaries share similar histologic, immunohistochemical, and molecular genetic profiles as compared to their soft tissue counterparts. The diagnosis of these tumors usually requires clinical, pathologic, and radiologic correlation and will often necessitate the use of ancillary studies to secure the diagnosis.