INTRODUCTION: Solitary fibrous tumors of the pleura (SFTP) are mesenchymal neoplasms of the pleural mesothelium usually arising from the visceral pleura. They are rare with only 850 cases having been reported in the literature so far. Both a benign and a malignant form of SFTP exist, in a ratio of 7:1. They are normally asymptomatic and are often incidentally detected radiologically except when their size produces compression-related clinical symptoms(such as dyspnea and cough.We report a case of SFTP masquerading as an extrapulmonary tumor of the posterior mediastinum.
CASE PRESENTATION: A 65 year old woman with a history of arterial hypertension and uterine fibromyomatosis was admitted to hospital for a scheduled operation of total hysterectomy. On routine preoperative evaluation, a slight bulging to the left of the superior mediastinal margin was noted on chest x-ray. The patient was otherwise asymptomatic. MRI revealed a paravertebral tumor of heterogeneous density, with a diameter of 4 cm in the upper left side of posterior mediastinum resembling a possible neurogenic tumor. After I.V. injection of gadolinium an enhancement of signal intensity was notified. An exploratory video-assisted thoracoscopy (VAT) confirmed the presence of a solid tumor of high mobility arising from the visceral pleura via a stalk at the left lung apex. The wedge resection was expanded to apical posterior segmentectomy. The tumor was finally removed thoracoscopically. It was, a well circumscribed partially encapsulated tumor, 4 cm in diameter with multinodular, whitish and firm appearance in cut section. Histology showed an architectural pattern characterized by a combination of alternative hypocellular and hypercellular areas separated from each other by thick bands of hyalinized somewhat keloidal collagen and branching haemangioericytoma –like vessels. Histologic differential diagnoses included SFTP, synovial sarcoma, cellular angiofibroma, neurofibroma and spindle cell lipoma. Immunohistochemical tests were positive for vimentin, CD34, CD 99, Bcl-2, and SMA, and negative for actin, desmin, S-100 and CD68. Final diagnosis, based on these tests was SFTP.
DISCUSSIONS: SFTPs most often originate in the visceral pleura (80–90%). The tumors which are almost always benign, most commonly arise as a pedanculated discrete mass usually attached to the visceral pleura as in the case we report. Their resection requires only a margin of normal lung tissue. Less commonly, SFTP arises as a sessile tumor developing from the parietal pleura of the chest wall, diaphragm, or mediastinum. These tumors are more prone to recur and require a wide local extrapleural excision. Occasionally this kind of tumors could masquerade mediastinal masses. To the best of our knowledge there have been no reported cases of visceral pleura origin of SFTPs masquerading mediastinal tumors as was the case of our patient. SFTPs are normally difficult to diagnose before surgery with fine needle aspiration. We believe that all undiagnosed thoracic tumors should first be evaluated by video-assisted thoracoscopy. The cavity can be fully explored, the neoplasm biopsied and diagnosed, and a decision made as to the best approach for excising (if possible) the tumorùall without the invasiveness of a thoracotomy. Tumors (whether lung tumors or not, malignant or not) can be resected using endoscopic methods by following the protocols of oncological surgery: extracting the excised tissue in a plastic bag to avoid seeding the chest wall.
CONCLUSION: SFTP are normally difficult to diagnose before surgery with fine needle aspiration. We believe that all undiagnosed thoracic tumors should first be evaluated by VAT with the neoplasm being biopsied and a decision made as to the best approach for excising.
DISCLOSURE: Stylianos Michaelides, None.