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Spontaneous decrease of a pilocytic astrocytoma in neurofibromatosis type 1.

A patient with type 1 neurofibromatosis was followed up with neuroimaging over a period of 12 years. A spontaneous decrease in the size of a histologically verified pilocytic astrocytoma was documented on serial CT and MR examinations. Subsequent studies showed the development of a lesion in the contralateral hemisphere with mass effect and contrast enhancement. Results of a biopsy disclosed normal brain tissue; follow-up imaging showed a spontaneous decrease in the size of this abnormality.