This 4-cm mature cystic teratoma of the ovary was found incidentally at the time of Caesarean section and removed. Like most ovarian teratomas (and unlike those of the testis) this one was benign, showing only mature tissues microscopically. In addition to the obvious cutaneous structures (giving rise to the hair seen here), histologically there was abundant neuroglia and even one neuron. Central nervous system tissue is very common in mature teratomas.
Source: Ed Uthman, MD. Public domain