Solitary Fibrous Tumor of the Pleura: Discussion

3 Mar

Solitary Fibrous Tumor of the Pleura: DiscussionSolitary fibrous tumor of the pleura is rarely diagnosed before surgical resection because cytology obtained by transthoracic needle aspiration is usually considered non-specific. Therefore, it is generally held that a thoracotomy is required for the diagnosis. We had the opportunity to study five cases by cytologic and histologic analysis of material obtained by transthoracic fine needle aspiration and Tru-Cut biopsy, respectively. This sampling method is routinely used at our institution to establish the diagnosis of parietal, pleural, or peripheral lung lesions with pleural contact. In the present report, we demonstrate that a confident preoperative diagnosis can be made with such a large-bore Tru-Cut needle biopsy. This is a minimally invasive procedure performed with the patient under local anesthesia. When carried out under fluoroscopic guidance, the procedure is fast (usually less than 10 min long overall). Because one performs Tru-Cut needle biopsies only when the lesion is abutting on the chest wall and the needle is not going through aerated lung parenchyma, one should not anticipate the occurrence of pneumothorax. According to Weynand and others, there has been no pneumothorax or other major complication of the procedure after 194 Tru-Cut needle biopsies in such circumstances (unpublished data). Since the procedure can be performed on an outpatient basis, its cost is very low (less than 200 USD in Belgium, including the cost of a CXR and pathologic analysis).

Obtaining a biopsy specimen is very helpful because the tumoral architecture is more readily appreciated and the differential diagnosis can be largely narrowed by immu-nohistochemistry. In particular, the anti-CD34 antibody has been claimed to be specific for solitary fibrous tumors. Although CD34 is expressed by various cell types, such as hematopoietic progenitor cells, endothelial cells, and mesenchymal tumor cells, its detection together with that of vimentin but not of cytokeratin in cells from a pleural tumor allows one to exclude the diagnosis of mesothelioma and of most other pleural tumors, such as carcinomas, fibrous histiocytomas, fibromatosis, fibrosarcomas, and synovial sarcomas.
Solitary fibrous tumors represent 5% of all pleural neoplasms. They can occur at any age with no sex predilection, and have not been associated with smoking habits or previous exposure to asbestos. They are often asymptomatic, but they can manifest themselves by nonspecific respiratory symptoms; rarely, they may be responsible for hypoglycemia or hypertrophic osteoarthropathy. CT or MRI, or both, usually show a well-delimited tumor with smooth contours; its content is sometimes heterogeneous.