[Primary lung hemangiopericytoma--a rare neoplasm with a long course of recurrence over many years]

Hemangiopericytoma (HPC) is a rare neoplasm arising from pericytes that occur mostly around smaller vessels. Up to now only about 100 cases have been reported to arise primarily in the lung. The behavior of pulmonary hemangiopericytomas is difficult to predict and all tumors should be considered potentially malignant, even though the criteria for malignancy are not well developed. The diagnosis of HPC is known to confound even experienced pathologist. Pericytes lack readily identifiable morphologic features, therefore hemangiopericytomas are often confused with other soft tissue tumors that may have hemangiopericytoma--like pattern. We report a rare case of primary HPC of the lung with an asymptomatic, long course of the disease. The diagnosis of hamartoma was established after the first operation. Subsequently, seven years later, a chest radiograph revealed new lesions. Histological examination, including immunohistochemistry lead to the final diagnosis of hemangiopericytoma. The small number of cases of primary pulmonary hemangiopericytoma makes it difficult to define the correct histopathological diagnosis especially without modern methods.