Embryonal tumor with multilayer rosettes (ETMR) is a rare and aggressive pediatric brain tumor. The tumor occurs primarily in young children, typically 4 years of age and younger. The tumor may occur in any part of the central nervous system, with the majority occurring in the top part of the brain (supratentorial), fewer in the lower part (infratentorial), and rare cases in the spinal cord.
The hallmark genetic finding of ETMR is the presence of an abnormality called C19MC amplification. C19MC amplification is generally felt to be critical to the biology of ETMR, but is not present in all cases of the tumor. Both ETMRs with and without C19MC amplification share similar biology and appear to have the same clinical behavior.
ETMR also displays overexpression of the RNA-binding protein LIN28A. LIN28 plays a critical role during embryonal development and may be important in the formation of cancer stem cells. Many therapies fail to fully eradicate cancer due to their inability to kill cancer stem cells, which go on to initiate tumor relapse, promote metastasis, and create resistance to chemotherapy and radiation therapy. The fundamental role of LIN28 in ETMR makes it an attractive biologic target for potential treatment.
ETMR follows an extremely aggressive course with overall survival times reported in the 5 to 30 month range. A medical paper of the French experience with these tumors detailed the cases of 38 children diagnosed with ETMR. These patients were found to have a 1-year event-free survival 36% and a 1-year overall survival of 45%. This data clearly demonstrates that new treatment approaches are needed for ETMR to change the course of this disease.