Fetal mediastinal tumor of neuroepithelial origin in a case of missed abortion.

We report a rare case of a primitive embryonal tumor discovered in the upper anterior mediastinum during routine autopsy of a macerated fetus at the 18th week of gestation. Our diagnosis was based on autopsy findings and histologic examination, which showed neuroepithelial differentiation of the tumor with frequent ependymal-type rosette formation; no structures of other germ cell layer origin were revealed. Additional positive immunohistochemical staining for CD56, CD57, and neurofilament protein confirmed the neural origin of the tumor, whereas the genetic analysis showed no MYCN gene amplification and no 11q23 deletion or rearrangement of EWS locus (22q12). Our findings exclude the possibility of teratoma and support the diagnosis of undifferentiated primitive tumor of neuroepithelial origin uncommonly located in the anterior mediastinum at the early 2nd trimester of gestation in a case of missed abortion.