Leptomeningeal dissemination of pilocytic astrocytoma at diagnosis in childhood: two cases report.

Pilocytic astrocytoma (PA) is a benign tumor that rarely spread along the neuraxis. At the moment there are no more than five cases of leptomeningeal dissemination (LD) from PA at diagnosis described in the literature. Different patterns of presentation or recurrence may be noted: local recurrence, malignant transformation, multicentric disease or metastatic disease. LD and multicentric disease can be distinct pathological entities. We report two cases and analyse literature, emphasizing leptomeningeal spread at presentation. Hydrocephalus, biopsy and parcial ressection are likely to be favorable factors to the occurrence of LD. Otherwise, LD may be part of natural history of PA, as evidenced by its ocurrence in non-treated cases.