Cyst wall enhancement in pilocytic astrocytoma: Neoplastic or reactive phenomena

Cystic pilocytic astrocytomas (CPA) consist of a mural nodule and an accomp anying cyst, which may prominently enhance on MRI after contrast administra tion. This raises the question whether an enhanced wall represents a tumor and thus should be resected together with the solid nodule, as radical tumo r surgery is associated with better prognosis. Until now, no systematic his topathological examinations of cyst walls have been reported in correlation with MRI, intraoperative appearance and postoperative clinical and MRI fol low-up. We present 3 patients with CPAs and brightly enhanced cyst walls on MRI. Because of the benign, transparent appearance of the cyst wall intrao peratively, it was biopsied but not resected, and only radical removal of t he nodule and its immediate surroundings was performed. Separate specimens taken from the cyst wall showed no tumor. MRI performed annually, up to 48- 56 months after surgery showed no recurrence of the cyst or the tumor. In s uch cases of CPA, we suggest that enhancement of cyst walls may represent r eactive rather than tumoral tissue, and may be left intact without risking worse prognosis. Mechanisms leading to cyst wall enhancement and the optima l surgical treatment are discussed. Copyright (C) 2000 S. Karger AG, Basel.