Primary Thoracic Hemangiopericytoma

Primary thoracic vascular tumors are uncommon; primary thoracic hemangiopericytomas are rare. Many of the early cases were unrecognized or were grouped under the general heading of vascular neoplasms. Because of the malignant potential, however, it is essential that hemangiopericytoma be recognized as a separate entity. Only 8 cases of primary thoracic hemangiopericytoma have appeared in the literature. Eleven additional cases are now presented, bringing the total to 19 (Table I). These include 4 hospitalized patients and 7 additional ones referred to Presbyterian Hospital (New York) for consultation and review.2 Hemangiopericytoma has no predilection for age or sex; it was congenital in 3 of Stout's patients. In cases of thoracic hemangiopericytoma, the age range was from ten to seventy-five years, with an average of forty-six years. Distribution Since its original pathologic description (38), hemangiopericytoma has been reported in various sites including the skin (33), superficial soft tissues (11, 13, 16, 17, 19, 23, 25, 29, 41), orbit (12, 14), retroperitoneum (1, 8), rectum (4, 18), sigmoid (3), omentum (37), jejunum (39), ileum (34, 35), uterus (15, 28, 40), bones, and meninges (6). This universal distribution is not surprising, since theoretically the tumor occurs wherever capillaries exist. Seybold et al. (31) and Balbaa and Chesterman (5) reviewed mediastinal vascular tumors in general. Seybold stated that they occurred in all parts of the mediastinum with equal frequency, but Balbaa found the anterior mediastinum more frequently affected especially in benign cases. Of the 19 thoracic hemangiopericytomas reviewed in this paper (including the 11 cases presently reported), 14 were primary in the mediastinum, 4 in the lung, and 1 in the pleura. Of the 14 mediastinal lesions, 3 were found in the anterior, 4 in the superior, 6 in the posterior, and 1 in the middle mediastinum. Incidence of Malignancy The incidence of the malignancy of hemangiopericytoma cannot be accurately judged because of the dearth of published cases and the insufficient data supplied in recorded instances. The fact that metastases may occur many years after the discovery and removal of the primary tumor forces us to reserve opinion in cases which have been reported as benign. The longest interval between removal of the primary thoracic tumor and recurrence was twenty-six years. In the majority of cases, long follow-ups were not obtained. Several tumors were regarded as benign on the basis of the gross surgical appearance, which suggested encapsulation, and subsequent histologic sections. It is difficult, however, to evaluate a capsule which, at times, may be partial and incomplete. In addition, these tumors do not reveal their true biological nature histologically. In the majority of those which subsequently proved malignant, no blood or lymph-vessel invasion could be seen histologically at the time of removal (27).