There is swelling, which can grow eyes, hair, teeth and muscle tissue

teratoma - a tumor that grows from the cells of the embryo. Most often found in the ovaries in women, testes in men, in the sacrococcygeal region in children, as well as in the brain.

The name comes from the Greek tumor teratos - «monster» and oma- «tumor." The reason is that the cause of the tumor - a violation of the normal development of the embryo tissue. This leads to the fact that the tumor contains the seeds of several bodies, uncharacteristic for this anatomical region. For example, ovarian teratoma may contain lymphatic tissue or muscle, next door to the hair follicles or the beginnings of the teeth or eyes. Thus, the surgical removal of a tumor of its appearance can be very unexpected, which obviously was the reason for the title of the tumor.

via factroom.ru