Medulloepitheliomatous component of immature teratoma lacks amplification at chromosome 19q13.42 locus: report of a case

Medulloepithelioma is a rare embryonal tumor of the central nervous system (CNS). Its distinct appearance is characterized by papillary and tubular arrangements of malignant singleto multi-layered columnar epithelium surrounded by an outer basement membrane. For years, this tumor has been viewed as an embryonal tumor that recapitulates the earliest stage of CNS development, namely the neural tube stage. Recently, amplification in 19q13.42 classified medulloepithelioma with ependymoblastoma and embryonal tumor with abundant neuropil and true rosettes (ETANTR) under the umbrella term embryonal tumor with multilayered rosettes (ETMR). Medulloepitheliomas typically occur in the cerebral hemispheres, but also uncommonly involve the cerebellum, cauda equina, presacral region, and eye. Medulloepitheliomatous elements can also arise in teratomas of the sacral and presacral region, raising a question as to how they compare to genuine CNS medulloepitheliomas that harbor the signature 19q13.42 amplification. We report a case of ventral sacrococcygeal immature teratoma with a prominent medulloepitheliomatous component arising in an 11-month-old girl as a ventral sacroccoccygeal tumor with intra-spinal extension from T10 to S3. Following surgical resection, the tumor recurred seven years later in the same location. The recurrent tumor consists almost exclusively of the medulloepitheliomatous component present in the original tumor. Additionally, the recurrent tumor lacks amplification in 19q13.42 by fluorescent in situ hybridization (FISH), suggesting that extracranial medulloepitheliomas are biologically different from conventional medulloepithelioma tumors despite their morphologic resemblance.