Diagnostic dilemmas in pulmonary mesenchymal tumors

Tumors of mesenchymal origin only rarely arise in the bronchopulmonary system and range from indolent neoplasms to highly malignant sarcomas. While many of these tumors occur more frequently outside of the thoracic cavity, there are some mesenchymal neoplasms that are unique to the lung, such as primary pulmonary myxoid sarcoma or clear cell stromal tumor of the lung. The diagnosis of these unusual neoplasms can be difficult, especially when dealing with small biopsy material or separating sarcomas from non-mesenchymal tumors with sarcomatoid morphology. Likewise, a metastatic process from a soft tissue primary should always be excluded before a diagnosis of primary pulmonary sarcoma can be confirmed. Fortunately, the increasing identification of distinct molecular aberrations in soft tissue, as well as pulmonary sarcomas, adds a significant diagnostic tool in this context. Since the treatment and prognosis for patients with pulmonary sarcomas varies greatly from those with bronchogenic carcinomas, comprehensive evaluation, to include immunohistochemical and molecular analysis, is not only essential for correct diagnosis, but also to predict patient outcome.