Adult Medulloblastoma: Clinicomolecular Spectrum, An Institutional Experience

Medulloblastoma is uncommon and molecularly lesser known in adults than their pediatric counterparts. This study aims to describe the clinicopathological and molecular characteristics of medulloblastoma in adults. Methods. The clinical, histopathological, and molecular features of 113 medulloblastoma patients of >18 years of age were reviewed. Molecular grouping (wingless pathway activated [WNT]-activated, sonic hedgehog activated [SHH]-activated, non-WNT/non-SHH, Group 3 and non-WNT/non-SHH, Group 4) was done by gene expression profiling. Results. The age-range was 19 to 59 years. The most common histoarchitecture was classic (64%), followed by desmoplastic/nodular (31%) and large cell/anaplastic (5%). The most common molecular group was SHH-activated (65%), followed by WNT-activated (14%), non-WNT/non-SHH, Group 4 (10%), and non-WNT/non-SHH, Group 3 (3%). All desmoplastic/nodular tumors were SHH-activated; while large cell/anaplastic had SHH-activated, WNT-activated and non-WNT/non-SHH, Group 3. TP53-mutant pattern of immunophenotype was observed in 7% (3 SHH-activated; 1 WNT-activated; 1 non-WNT/non-SHH, Group 3; 2 indeterminate). Within the SHH-activated group, TP53-mutant pattern immunophenotype was noted in 3 tumors and 1 was MYCN-amplified. In the WNT-activated group, both monosomy 6 and CTNNB1 mutation were seen in 3 tumors and 3 each had an isolated alteration. Conclusion. SHH-activated medulloblastoma is the most common group and WNT-activated is not rare in adults. Non-WNT/non-SHH, Group 3 though rare is not nonexistent in adults.