Novel neoplasms associated with syndromic pediatric medulloblastoma: integrated pathway delineation for personalized therapy

Calcifying pseudoneoplasm of the neuraxis progressing to G5/PDGFRA subgroup glioblastoma in a United States Army veteran with a history of head trauma and germline POT1 and EPHB2 mutations: illustrative case

BACKGROUND

Trauma-associated glioblastoma has been previously described, albeit without molecular characterization.

OBSERVATIONS

The authors show the integrated clinical/pathologic/molecular analysis of a glioblastoma developing 43 years after head trauma sustained by a United States veteran. An epileptogenic benign lesion developed at the trauma site, followed 34 years later by a calcified lesion diagnosed as calcifying pseudoneoplasm of the neuraxis (CAPNON) that recurred 9 years later as glioblastoma with heterotopic/metaplastic ossification. Genomic analysis showed novel germline mutations in the telomere maintenance factor POT1 p.W184* and receptor tyrosine kinase (RTK) EPHB2 p.W792*. The somatic alterations included second-hit POT1 p.D163Y mutation, CDKN2A/2B homozygous loss, DNMT3A mutation and PDGFRA amplification, classifying this glioblastoma in the G5/PDGFRA molecular subgroup. Proliferation markers, PDGFRA, MAPK feedback inhibitors, and EPHB1 showed high expression, whereas EPHB3 and EPHA7 showed the highest expression of all glioblastomas. Following gross-total resection, the patient received adjuvant radiotherapy and temozolomide and died 16.3 months later.

LESSONS

This is the first report of CAPNON progression to glioblastoma and of molecularly characterized glioma occurring decades after head trauma. A multifactorial etiology including genetic predisposition and posttraumatic repair is hypothesized. The discussion presents possible roles of EPH RTKs in posttraumatic repair and CAPNON, and of POT1 and PDGFRα in subsequent progression to glioblastoma. https://thejns.org/doi/10.3171/CASE25152.

Translation into Clinical Practice of the G1-G7 Molecular Subgroup Classification of Glioblastoma: Comprehensive Demographic and Molecular Pathway Profiling

Glioblastoma is the most frequent and malignant primary neoplasm of the central nervous system. In a recent breakthrough study on a prospective Discovery cohort, I proposed the first all-inclusive molecular classification of glioblastoma into seven subgroups, G1-G7, based on MAPK pathway activation. New data from a WHO-grade-4 diffuse glioma prospective Validation cohort offers, in this study, an integrated demographic-molecular analysis of a 213-patient Combined cohort. Despite cohort differences in the median age and molecular subgroup distribution, all the prospectively-acquired cases from the Validation cohort mapped into one of the G1-G7 subgroups defined in the Discovery cohort. A younger age of onset, higher tumor mutation burden and expanded G1/EGFR-mutant and G3/NF1 glioblastoma subgroups characterized the glioblastomas from African American/Black relative to Caucasian/White patients. The three largest molecular subgroups were G1/EGFR, G3/NF1 and G7/Other. The fourth largest subgroup, G6/Multi-RTK, was detailed by describing a novel gene fusion ST7-MET, rare PTPRZ1-MET, LMNA-NTRK1 and GOPC-ROS1 fusions and their overexpression mechanisms in glioblastoma. The correlations between the MAPK pathway G1-G7 subgroups and the PI3-kinase/PTEN, TERT, cell cycle G1 phase and p53 pathways defined characteristic subgroup pathway profiles amenable to personalized targeted therapy. This analysis validated the first all-inclusive molecular classification of glioblastoma, showed significant demographic and molecular differences between subgroups, and provided the first ethnic molecular comparison of glioblastoma.

Adult glioblastoma with Lynch syndrome-associated mismatch repair deficiency forms a distinct high-risk molecular subgroup

Glioblastoma is the most frequent and malignant primary brain tumor. Although the survival is generally dismal for glioblastoma patients, risk stratification and the identification of high-risk subgroups is important for prompt and aggressive management. The G1-G7 molecular subgroup classification based on the MAPK pathway activation has offered for the first time a non-redundant, all-inclusive classification of adult glioblastoma. Five patients from the large, 218-patient, prospective cohort showed germline mutations in mismatch repair (MMR) genes (Lynch syndrome) and a significantly worse median survival of 3.25 months post-surgery than those from the G1/EGFR and G3/NF1 major subgroups, or from the rest of the cohort adjusted for age. These rare tumors were assigned to a new subgroup, G3/MMR, a G3/NF1 subgroup spin-off, as they generally show genomic alterations leading to RAS activation, such as NF1 and PTPN11 mutations. An integrated clinical, histologic and molecular analysis of the G3/MMR tumors showed distinct characteristics as compared to other glioblastomas, including those with iatrogenic high tumor mutation burden (TMB), warranting a separate subgroup. Prior history of cancer, midline location or multifocality, presence of multinucleated giant cells (MGCs), positive p53 and MMR immunohistochemistry, and specific molecular characteristics, including high TMB, MSH2/MSH6 alterations, biallelic TP53 Arg mutations and co-occurring PIK3CA p.R88Q and PTEN alterations, alert to this high-risk G3/MMR subgroup. The MGCs and p53 immunohistochemistry analysis in G1-G7 subgroups showed that one in 7 tumors with these characteristics is a G3/MMR glioblastoma. The FDA-approved first-line therapy for many advanced solid tumors consists of nivolumab-ipilimumab immune checkpoint inhibitors. One G3/MMR patient received this regimen and survived much longer than the rest, setting a proof-of-principle example for the treatment of these very aggressive G3/MMR glioblastomas.