547P - Clinicopathological and molecular study of embryonal tumours with multilayered rosettes

Background

To analyze clinicopathological features of ETMRs.

Methods

A total of 14 cases of ETMRs from 2016 to 2021 in Xuanwu Hospital of Capital Medical University were retrospectively summarized. The clinical and imaging characteristics, pathological and molecular characteristics were analyzed, and the related literature was reviewed.

Results

All 14 patients (6 males and 8 females) aged from 9 months old to 3 years old (mean 2 years) mainly had a history of headache or/and vomiting. Twelve tumors were supratentorial and two infratentorial, seven of which occurred in the frontal lobe. The MRI findings showed that the lesions were located in the third ventricle, and the enhanced MRI showed abnormal enhancement signals. The MRI enhancement all showed an abnormal enhancement signal. Pathological finding showed that 12 cases had displaying the morphological characteristics of ETMR. The distribution of tumor cells is sparse and uneven, and some cells arrange in multiple layers and grow around blood vessels, partially forming a "Homm-rett group" structure, island-like structure can be seen. IHC showed Syn and Lin28a were immunopositive in all 14 cases (14/14). GFAP and Olig-2 were partially immunopositive in 3 cases (3/14). EMA was dot-and/or-ring immunopositivity in 2 cases (90%, 2/14). At the same time, there was a case immunopositive for H3K27M, with the loss of H3K27me3. 12 ETMRs were available to detect C19MC and Dicer1 gene mutation. 11 in 12 (88.9%) were found to have C19MC amplification, and one have Dicer1 mutation as well as H3K27M mutation. Among the 14 patients after surgery, All 10 patients received adjuvant radiotherapy/chemotherapy,Progression-free survival was 6.2 months, and overall survival was 11 months.

Conclusions

ETMRs have relatively distinguishing clinical and histopathological features. C19MC alteration and Dicer1 gene mutation, can be considered as useful biomarkers for the diagnosis and differential diagnosis, and provide a direction for targeted therapy in the future.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.