Well-developed Cerebellum in an Ovarian Mature Teratoma From a Pregnant Female.

Teratomas are the most common neoplasm of the ovary, comprising over half of all diagnosed tumors in patients under 50. Most lesions are classified as benign mature teratomas and are histologically defined by the presence of mature tissues from one or more of the embryological germ layers: ectoderm, mesoderm, and endoderm. Neuroectodermal derivatives, including glia, neurons, ependymal cells, and meninges are present in a third to half of mature teratomas. Although teratomatous tissue elements are typically arranged in a haphazard fashion, well-developed and organized embryonic organ structures have been rarely reported and often with limited histologic, clinical, or gross characterization. In this report, we describe the case of an ovarian mature cystic teratoma identified in a pregnant female which exhibited remarkably well-developed posterior fossa structures including lobated and foliated cerebellum with appropriate anatomic organization and associated brainstem, ventricular, and meningeal structures.