Pleomorphic Xanthoastrocytoma

Abstract

In 1973, Dr. John Kepes reported Three cases of superficial temporal lobe tumors occurring in 11- and 12-year-old children (1). These tumors involved both the leptomeninges and superficial cerebral cortex, were composed of spindle shaped and multinucleated giant cells containing abundant lipid droplets, and were rich in reticulin fibers that surrounded individual tumor cells. Based on their location and these histopathologic features, they were considered to represent fibrous xanthomas of the meninges invading the brain. It was noted, however, that in less lipidized areas of the tumors, the tumor cells resembled astrocytes. With the development of antibodies to glial fibrillary acidic protein in the late 1970s, Drs. Kepes and Rubinstein went back to these cases (as well as nine others), and reclassified them as astrocytic tumors, suggesting the name “pleomorphic xanthoastrocytoma” (PXA) (2). In this landmark article, Drs. Kepes, Rubinstein, and Eng described 12 supratentorial astrocytomas occurring in patients ranging from 7 to 25 (average 12) years of age. The tumors were superficial, usually involved the leptomeninges, and most often were grossly cystic. The cardinal histopathologic features described in the earlier study (pleomorphism, cytoplasmic lipidization, and dense pericellular reticulim) were reemphasized, and several other important microscopic features were defined, including eosinophilic granular bodies, variable numbers of lymphocytes and plasma cells, a paucity of mitotic figures, and the absence of necrosis (Figs. 8-1 through 8-5). The authors suggested that the tumors may have arisen from subpial astrocytes, as these cells were known to be normally invested by basal laminae that appear to be a product of the astrocytes themselves, and not that of the pial elements. Most importantly, they stressed the relatively favorable biologic behavior of these tumors, as most of their patients were alive at the time of follow-up, which for several was 16 to 25 years after diagnosis.