Clinical behavior of solitary fibrous tumors of the pleura

Background. Solitary fibrous tumors of the pleura are rare and present unpredictable clinical behavior. Methods. Between 1981 and 1998, 11 solitary fibrous tumors of the pleura were resected in 10 patients at the University Hospital of Geneva. Their clinical behavior and outcome were reviewed. Results. Seven tumors arose from the visceral pleura, and three arose from the parietal pleura. Tumors arising from the parietal pleura were revealed to be more difficult to resect than those from the visceral pleura because of their size and adhesion to the chest wall requiring extrapleural resection. Eight tumors showed benign features, whereas two showed distinct features of malignity. One additional patient presented marked pleomorphism that could represent an intermediate form before frank malignity. Four tumors had been followed expectandly for 2 to 10 years before surgery. Although three enlarged rapidly, no signs of malignity were observed on histological examination. All patients are alive, from 2 months to 14 years after surgery (mean 55 months). In one case, however, a malignant tumor recurred 6 years after resection of a benign variant. Conclusions. Although histologically benign, solitary fibrous tumors of the pleura may enlarge rapidly and occasionally transform into malignant variants after several years. Therefore, complete surgical resection and long-term follow-up is recommended for all patients.