Recurrences of cerebellar astrocytomas: a violation of Collins' law.

Cerebellar astrocytomas generally carry an excellent prognosis when managed with surgical treatment alone. However, these tumors may violate Collins' Law in two opposite ways: by recurring late or by being "cured" with incomplete excision. In a study of 41 cases of cerebellar astrocytoma and a review of the literature, no gross or microscopic factors that correlated with either of these two outcomes could be identified other than brain-stem involvement. The effect of radiation therapy in the treatment of primary or recurrent cerebellar astrocytomas was not detectable when analyzed the same way. Malignant recurrence of cerebellar astrocytoma and primary malignant tumors of the cerebellum are so rare that the possibility should not be taken as a reason to substitute radiation therapy for surgical excision repeated as necessary.