Adult medulloblastoma-Clinico-molecular spectrum, an institutional experience

Medulloblastoma (MB) is uncommon and molecularly lesser known in adults than their pediatric counterparts. Purpose: To describe the clinic-pathological and molecular characteristics of MB in adults. Methods: We reviewed the clinical, histopathological, and molecular features of 113 cases of MB in patients >18 years of age. Molecular grouping (WNT-activated, SHH-activated, non-WNT/non-SHH, group 3 & non-WNT/non-SHH, group 4) was done by gene expression profiling (GEP). Results: Age range was 19-59 years. The most common histology was classic (51.3%), followed by desmoplastic/nodular (D/N) (23.9%), NOS (12.4%), paucinodular (7%), and large cell/anaplastic (LC/A) (5.4%). The most common molecular group was SHH-activated (64.8%), followed by WNT-activated (14.3%), non-WNT/non-SHH group 4 (9.9%), and group 3 (3.3%). All D/N cases were SHH; while LCA had SHH, WNT and group 3. p53-mutant pattern of immunopositivity was observed in 6.6% (3 – SHH; 1- WNT; 1- group 3). Within the SHH group, p53 mutant pattern was noted in 5 cases and one case was MYCN-amplified. Disease progression was observed in 40% of SHH cases. In WNT, both monosomy 6 and CTNNB1 mutation were seen in 3 and 3 cases each had an isolated alteration. Anaplastic histology and TP53 mutation did not affect survival of WNT. Conclusion: SHH-MB is the most common group and group 3, though rare, is not non-existent in adults.