Circumscribed Pilocytic Astrocytoma Including Pilomyxoid and Intermediate Pilomyxoid Variants - A Single Institutional, Retrospective Study.

Classical pilocytic astrocytoma (PA) is the most common childhood glioma that corresponds to WHO Grade I. These tumors are generally well circumscribed and are also observed in adult population. Due to diverse histomorphological patterns, a subtype was added by WHO in 2007 that was referred to as pilomyxoid astrocytoma (PMA). Initially, it was thought that the clinical behavior of PMA was more aggressive. Recent WHO classification (2021) has, however, not assigned a grade to PMA due to insufficient data in medical literature. Fourteen cases of PA, four cases of PMA, and two cases of intermediate pilomyxoid tumor (IPMT) constituted the study group. Majority of the patients were in pediatric age group (PA 78%; PMA 100%), mean age of PMA was 10 years vs PA was 16 years. Cerebellum was the commonest location for both PA and PMA. Tumor dimension greater than 5 cm was noted in 57% PA cases and 50% PMA cases. Solid-cystic mass lesion was observed in 86% PAs and 75% PMAs. IPMT tumor with dual morphology was noted, one each in pediatric and adult patient. Gross total resection of the tumor was achievable in 78% and 75% of PA and PMA, respectively. Follow-up duration ranged from 6 to 180 months, and recurrence was noted in 2 PA patients and one PA patient died after 1 year of treatment. Despite the varied morphological features of PA and PMA, considerable overlap was noted in clinico-radiological behavior, postoperative outcome, certain morphological parameters, and immunomarker expression in tumor cells among the two subtypes. Designating PMA as a higher grade tumor cannot be justified presently; additional multidisciplinary studies are needed for final decisiveness.