Background: Solitary fibrous tumors of the pleura (SFTP) are rare. The aims of this study were (1) to characterize their clinicopathological features more precisely; (2) to determine whether an immunohistochemical (IHC) study can be helpful in distinguishing benign from malignant SFTPs; and (3) to provide more complete information to better predict prognosis. Methods: Microscopic examinations of tumorous specimens from 15 patients were repeated and the tumors were reclassified. In addition to evaluating clinicopathological variables, expressions of p16, p53, Ki-67, CD-117, estrogen receptor (ER), and progesterone receptor (PR) biomarkers were studied and their clinicopathological and prognostic significance analyzed. Results: Of the 15 enrolled patients (mean age 57 years; 8 men and 7 women), 8 were symptomatic when diagnosed. Eight patients underwent CT-guided needle biopsies before surgery and two had positive findings. All cytologic studies of pleural effusion were negative for malignant cells. Complete pleural resection with adequate safe margins was performed for all patients. Eleven cases proved to have benign tumors and 4 had malignancies. Local recurrence occurred in 3 cases and distant metastasis in one. Conventional factors, including tumor size, tumor shape, symptomatic presentation, and histological type did not affect prognosis. Interestingly, p16 expression was significantly associated with tumor recurrence (p = 0.009). Conclusion: Complete pleural resection with adequate safe margins can achieve satisfactory outcomes in a majority of cases, but long-term follow-up for all patients is recommended due to the potential for late tumor recurrence. Conventional clinicopathological variables do not affect prognosis. However, IHC studies of the CD-34 and bcl-2 biomarkers can be important for further differential diagnosis, and p16 expression can be used to predict tumor recurrence.
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