Cerebellar astrocytomas. Part II. Pathologic features indicative of malignancy.
The pathologic features which denote poor clinical outcome in a series of 112 cerebellar astrocytomas seen at The Radcliffe Infirmary, Oxford between 1938 and 1984 have been described. These have been reviewed in relation to the findings of numerous other reports in the literature. The conclusions reached are as follows: Pleomorphism: A substantial proportion of cerebellar astrocytomas display significant nuclear and cytoplasmic size variation. This is particularly common after the age of ten. Markedly pleomorphic tumors are, moreover, associated with a very short survival time. Mitotic Figures: Mitotic figures are seen in 8.5% of cerebellar astrocytomas but are found in large numbers, in only 1.1% of cases. They are more common in adults and in totally solid tumors. The presence of any mitotic figures in cerebellar astrocytomas is associated with a marked reduction in survival to death and also a noticeable increase in the rate of recurrence. Cellularity: Marked focal hypercellularity is seen in 13.2% of cerebellar astrocytomas and is especially common in childhood tumors. When marked, it is associated with a significant reduction in survival time to death. Desmoplasia: Desmoplastic reactions adjacent to tumor are seen in one-half of all cerebellar astrocytomas but are only marked in 16% of cases. When marked, however, they are associated with a reduction in overall survival time. Perivascular Pseudorosettes: These are seen in 80.9% of all cerebellar astrocytomas. When found in large numbers, they are more commonly seen in children than in tumors with a mixed cystic and solid form. Their appearance is associated with a favorable outcome when found in association with microcystic change and endothelial hyperplasia but when found in isolation they are associated with poor survival. Necrosis: Small necrotic foci are found in 16.8% of cases. Markedly necrotic tumors are very rare and are more commonly seen in patients with short histories and associated with very poor outcome. Definite malignant features: 1. Pleomorphism, if marked; 2. Mitotic figures, in any number; 3. Cellularity, if marked; 4. Desmoplasia (probably) if marked; 5. Perivascular pseudorosettes, in isolation without microcystic change and endothelial hyperplasia; 6. Necrosis, if marked. Primary malignant cerebellar astrocytomas: These tumors are rare and represent cerebellar astrocytomas with one or more areas containing the aforementioned malignant features. Primary glioblastomas of the cerebellum: These tumors are also rare and resemble both clinically and pathologically glioblastomas found in other parts of the nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)