PRIMARY INTRACRANIAL PLEOMORPHIC ANGIOLEIOMYOMA - A NEW MORPHOLOGIC VARIANT - AN IMMUNOHISTOCHEMICAL AND ELECTRON-MICROSCOPIC STUDY

Background. Angioleiomyomas usually are benign subcutaneous neoplasms that occur most often in extremities of middle-aged individuals. Very few cases have been described in other locations; none along the neuro axis. Am intracranial example of angioleiomyoma displaying unusual mor phologic features not seen in the typical peripheral variants of this tumor is described. Methods. The tumor was studied with conventional h istology, immunohistochemistry with morphometric calculation of prolif eration index, immunoelectron microscopy, and DNA flow cytometry. Resu lts. The tumor was composed of large epithelioid and pleomorphic cells filled with intermediate filaments positive for desmin and vimentin. Scattered cells also expressed myosin and muscle-specific actin. Smoot h muscle cell differentiation was confirmed by ultrastructural demonst ration of subplasmalemmal dense bodies, attachment plaques, and discon tinuous basal lamina. The proliferation index with proliferating cell nuclear antigen (PCNA) monoclonal antibody was 75.78%, whereas it was only 4.22% with Ki67 monoclonal antibodies adopted to paraffin materia l (MIB-1). Conclusion. The tumor represents a unique morphologic varia nt of a pleomorphic angioleiomyoma. Cellular pleomorphism and a strong reaction for PCNA in numerous cells suggested that the lesion was mal ignant. However, the absence of mitotic figures, a small number of Ki6 7-positive cells, a diploic DNA pattern, and a low proliferation index in flow cytometry all supported the concept that this neoplasm repres ented an unusual histologic variant of benign angiogenic leiomyoma. En capsulation and demarcation of the surgical specimen and the survival of the patient for more than 4 years without recurrence after resectio n support this interpretation.