Mature ovarian cystic teratoma with a highly differentiated homunculus: a case report

Mature ovarian cystic teratomas, which are commonly observed benign ovarian tumors, consist of ectodermal, mesodermal, and endodermal components that are generally disorganized. In this report, we document a case in which the solid portion of an ovarian teratoma demonstrated considerable differentiation, forming a doll-like structure.

A 25-year-old virginal Japanese woman underwent surgery for an ovarian tumor that was diagnosed as a mature teratoma. A solid mass within the tumor was found to have a head, trunk, and extremities. Consequently, this mass was diagnosed as a mature fetiform teratoma (homunculus). Brain, eye, spinal nerve, ear, teeth, thyroid gland, bone, bone marrow, gut, trachea, blood vessels, and phallic cavernous tissue were confirmed microscopically. Distinctive features were the clear anterior-posterior, ventral-dorsal, and left-right axes, with a spatially well-organized arrangement of the organs. An eye was located on the front of the head, a spinal nerve lay dorsal to the spinal bones, the thyroid gland was anterior to the trachea, and the gut was deep inside the trunk.

These findings indicate that the information necessary for organization of the body plan may be conserved and transmitted, even with parthenogenesis. Mature cystic teratomas of the ovary are mostly benign and do not always attract detailed attention. However, precise analyses of such tumors may significantly enhance our understanding of both parthenogenetic and normal human development.