ABSTRACT The 2021 WHO Classification of Tumors of the Central Nervous System incorporates integrated molecular diagnostics into the classification of diffuse gliomas; however, access to comprehensive molecular testing remains limited in some settings. This study retrospectively evaluated grade‐associated patterns of PCR‐based loss of heterozygosity (LOH) and microsatellite instability (MSI) in a historical, morphology‐defined cohort of diffuse astrocytic gliomas from the pre‐IDH era. LOH and MSI analyses were performed using 14 LOH and 5 MSI microsatellite markers in 40 archival diffuse astrocytic gliomas, including 12 diffuse astrocytomas, NOS (WHO grade 2), 15 anaplastic astrocytomas, NOS (WHO grade 3), and 13 glioblastomas, NOS (WHO grade 4), collected between 1997 and 2002 prior to the availability of IDH immunohistochemistry. LOH‐high (LOH‐H) was defined as LOH involving three or more of the seven microsatellite markers examined at each locus, and MSI‐high (MSI‐H) as instability at two or more of the five markers. LOH was detected in 77.5% of tumors. LOH‐H at 10q23 ( PTEN ) correlated significantly with WHO grade (8.3%, 40.0%, and 61.5% in grades 2, 3, and 4, respectively; p = 0.022) and distinguished high‐grade from low‐grade tumors ( p = 0.015). LOH‐H at either 10q23 or 17p13 ( TP53 ) was observed in 67.9% of high‐grade tumors compared with 25.0% of grade 2 tumors ( p = 0.013). MSI and MSI‐H rates were 17.5% and 10.0%, respectively. Three of the four MSI‐H tumors lacked concurrent LOH‐H; given the small number of MSI‐H tumors, this observation is preliminary and should not be interpreted as evidence of distinct genomic instability pathways. LOH‐H at 10q23, alone or in combination with 17p13, was associated with higher morphology‐based WHO grade, whereas 17p13 LOH alone showed no significant grade association. Because IDH mutation status could not be determined, these findings should not be extrapolated to contemporary WHO‐defined astrocytic gliomas; whether these findings apply to molecularly defined gliomas would require validation.
ABSTRACT Large cell/anaplastic medulloblastoma is a high‐risk variant whose histopathological diagnosis can be challenging. We analyzed 12 pediatric cases enriched for LC/A morphology, with centralized review available for 11. In this deliberately selected, diagnostically challenging series, institutional and central LC/A versus non‐LC/A assessments were discordant in 36% (4 of 11), illustrating the difficulty of applying the LC/A designation rather than a general estimate of inter‐observer reproducibility. DNA methylation profiling was performed using four classifiers: Heidelberg CNS Tumor Methylation Classifier, Methylscape Analysis, EpiDiP, and the MAGIBU classifier, which applies a UMAP‐based distance approach. Tumor classification was largely concordant across platforms, identifying two WNT ‐activated medulloblastomas, eight non‐ WNT /non‐ SHH medulloblastomas, and one tumor reclassified as an embryonal tumor with multilayered rosettes. One misclassification occurred with EpiDiP, where an SHH ‐activated medulloblastoma aligned with the normal cerebellar cortex reference profile. Copy number analysis revealed MYC amplification in two non‐ WNT /non‐ SHH tumors, chromosome 6 loss in both WNT ‐activated cases, and isochromosome 17q in one MYC ‐amplified non‐ WNT /non‐ SHH tumor. Adjunctive molecular data for a subset of cases were obtained from PedcBioPortal. The reclassified tumor lacked canonical molecular alterations but harbored additional CTNNB1 and TP53 variants whose contribution to its pathogenesis remains uncertain. One WNT ‐activated medulloblastoma also carried a CTNNB1 variant. The MAGIBU classifier correctly identified the ETMR case, classified all remaining tumors as medulloblastomas, and showed concordant subgroup assignment with the Heidelberg CNS Tumor Methylation Classifier and Methylscape Analysis, including the SHH ‐activated case misclassified by EpiDiP. On external validation across four independent medulloblastoma cohorts ( n = 1063), MAGIBU achieved 98.5% family‐level recall and 96.4% subclass‐level recall. In conclusion, our findings indicate that, in these diagnostically challenging, LC/A‐enriched cases, morphology‐based diagnostic assessment can be inconsistent. DNA methylation profiling serves to refine tumor reclassification and ensure accurate risk stratification. Interpreting each tumor across complementary classifiers provides a triangulation that enhances diagnostic robustness.
Central nervous system germ cell tumors are uncommon and include germinomas, teratomas, and other nongerminomatous germ cell tumors. Mature teratomas are usually cured by complete resection, but rare patients later develop a histologically distinct malignant germ cell tumor. We report a man who presented at age 20 years with a cystic pineal lesion. Gross-total resection at age 21 years showed a mature teratoma with bronchogenic differentiation and no overt immature or malignant component on H&E. Serial postoperative MRI for 3 years showed no recurrence. Eleven years after surgery, he developed headache, gait disturbance, and confusion due to a 4.6-cm pineal mass with obstructive hydrocephalus. Serum alpha-fetoprotein was normal, whereas beta-human chorionic gonadotropin (β-hCG) was elevated. The resected tumor showed sheets of large round cells with clear cytoplasm and dense lymphocytes. Immunohistochemistry demonstrated strong nuclear OCT4 and SALL4 and membranous c-KIT, with focal β-hCG-positive syncytiotrophoblastic giant cells. No nongerminomatous germ cell tumor component was identified, supporting a diagnosis of germinoma with focal syncytiotrophoblastic giant cells. After this diagnosis, retrospective evaluation of the initial tumor showed multifocal, patchy OCT4 immunoreactivity in scattered cells along the ciliated respiratory-type epithelial lining. SALL4, c-KIT, and PLAP were focally positive in corresponding regions. These findings raised the possibility of an occult germ cell marker-positive population, although no discrete expansile germinoma component was identified. This case illustrates that metachronous germinoma can develop after a long disease-free interval following resection of a mature teratoma and highlights the value of retrospective pathologic evaluation and long-term surveillance.
Glioblastoma is the most common primary malignant central nervous system (CNS) tumor; however, its microenvironment, including tumor-associated microglia/macrophages (TAMs), is not fully understood. Although ionized calcium-binding adaptor molecule 1 (IBA-1) is expressed in various microglial phenotypes in the healthy human brain, CD163 is a marker of activated/phagocytic microglia. Tissues from 34 patients with glioblastoma were analyzed, and 17.6% of cases were CD163-dominant. CD163-dominant patients showed better overall survival than IBA-1-dominant patients (p = 0.019). CD163 dominance was identified as an independent prognostic factor for overall survival (hazard ratio [HR], 0.17; p = 0.011). Compared with the IBA-1-dominant group, CD163-dominant tumors showed more CD4-positive cell infiltration (p = 0.005), fewer ameboid TAMs (p = 0.021), and fewer non-microvascular proliferation (non-MVP) vessels (p = 0.012). No significant differences were found in patient characteristics, such as age, sex, tumor location, or extent of resection. The CD163-to-IBA-1 ratio of TAMs is a significant independent prognostic factor in glioblastoma, suggesting that the activation status of these cells and their interactions with the vascular endothelium and T cells influence tumor progression. These findings highlight TAMs as potential therapeutic targets for glioblastoma.
