Well formed teeth visible in a mature cystic teratoma(dermoid cyst) of the ovary. The tissues of a teratoma, although normal in themselves, may be quite different from surrounding tissues and may be highly disparate; teratomas have been reported to contain hair, teeth, bone and, very rarely, more complex organs or processes such as eyes,torso, and hands, feet, or other limbs.
Photo credit: lunar caustic
thefancywalrus 