What question did this study set out to answer?

The aim is to investigate the characteristics and outcomes of pediatric brainstem embryonal tumors known as ETMRs.

March 14, 2026Open Access

ETMR-12. Rare Brain Tumor Consortia (RBTC) case series: Insights into primary brainstem ETMRs, a rare and aggressive tumor of childhood

Key Points

The aim is to investigate the characteristics and outcomes of pediatric brainstem embryonal tumors known as ETMRs.
Retrospective case series analysis of 21 pediatric patients with brainstem ETMRs, submitted to the RBTC.
Assessment included radiological features, histopathological diagnosis, and treatment outcomes.
Molecular analysis was conducted to evaluate C19MC alterations.
Median progression-free survival was 4 months; overall survival was less than 13 months.
Among 21 patients, only one had long-term survival after complete surgical resection and intensified treatment.
Histopathological diagnoses varied, requiring careful molecular analysis for accurate classification.

Abstract

Abstract Brainstem tumors account for 10-20% of all pediatric brain tumors, amongst these gliomas are the most common brainstem tumors. Our study examines the occurrence of non-gliomatous brainstem tumors, specifically embryonal tumors with multilayered rosettes (ETMRs). ETMRs are newly described, rare aggressive tumors of infancy, characterized by C19MC alterations. A recent largescale study by the RBTC shows ETMRs can arise anywhere in the brain, most frequently in the cerebrum (60%), followed by cerebellum (18%) and other midline structures (6%). Amongst the 165 molecularly confirmed ETMRs submitted to the RBTC, 21 cases presented with brainstem primaries (BS-ETMRs). Many of these radiologically mimic diffuse intrinsic pontine gliomas with typical and atypical features with dorsally exophytic growth. Median age at diagnosis was 27 months (range 16-75months), with no observed gender predilection. Nearly all patients presented with neurological symptoms, including cranial nerve palsies, long tract signs, and gait disturbance. Most cases were localized at diagnosis, with only one presenting with disseminated disease. Of 21 patients, 11(52%) underwent partial resection while 7(33%) had a biopsy. Complete tumor resection was achieved in only one case. Histopathological diagnosis varied between ETANTR, ETMR and PNET. Molecular analysis showed majority of cases were C19MC-altered. Two patients received upfront palliative care, while 19 were treated with curative intent, using heterogenous combination of chemotherapy with and without radiotherapy. Outcomes were poor, with a median progression-free survival of 4 months and overall survival of less than 13 months. All but 4 patients experienced local progression. The only long-term surviving patient (OS 5years) underwent complete resection, intensified chemotherapy, and radiotherapy. Review of the literature identified seven additional non-duplicate molecularly confirmed cases, none of which are long-term survivors. Primary brainstem ETMRs are rare, highly aggressive disease associated with a poor prognosis. Prompt diagnosis and multimodal therapy with maximal safe surgical resection are essential to improving outcomes.

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