[Problems entailed in the definition and pathology of anaplastic astrocytoma]

Three-tiered system dividing supratentorial astrocytic neoplasms into the astrocytoma, anaplastic (malignant) astrocytoma and the glioblastoma multiforme has been widely used. However, the pathology of anaplastic astrocytoma is defined in different ways according to different classifications. A total of 42 biopsy specimens from 35 cases diagnosed as anaplastic astrocytoma were reviewed pathologically and their features were correlated with a follow-up clinical study to discuss the prognostic usefulness of the subdivision of anaplastic astrocytoma. In WHO classification, anaplastic astrocytoma is defined as "astrocytoma containing areas of anaplasia". Follow-up study of 7 cases with the histology as such revealed that 5 cases had survived more than one year and seven months. The other 28 cases showed a varied histology and were subclassified into an astrocytoma in which moderately anaplastic cells are found throughout the tumor, an astrocytoma formed by anaplastic fusiform cells, an astrocytoma composed of predominantly rounded anaplastic cells, and a pleomorphic astrocytoma with or without intracytoplasmic hyaline inclusions. A follow-up study of cases with these types of astrocytoma disclosed death in 15 cases within one year and 7 months following the first surgery and that three cases displayed typical histological features of glioblastoma at autopsy. It is considered that there would be a considerable overlap between the group of anaplastic astrocytoma and that of glioblastoma, if we use the term "anaplastic astrocytoma" in a broader category.