'A 22-year-old woman sought medical care for a lesion in the plantar region of her left foot, a well-formed nipple surrounded by areola and hair. Microscopic examination of the dermis showed hair follicles, eccrine glands, and sebaceous glands. Fat tissue was noted at the base of the lesion. Clinical and histopathologic findings were consistent with the diagnosis of supernumerary breast tissue, also known as pseudomamma. To our knowledge, this is the first report of supernumerary breast tissue on the foot.

These supernumerary breasts can pop up all over the place, including the face, back, and thigh (and foot, obviously). They can be functionally complete, and can even lactate. The authors report some weak and sometimes contradicted associations with other oddities, but no causal mechanism is known. These cases of autonomous self-organization and recruitment of organs are extremely interesting—it suggests that a breast would be a fairly easy tissue to grow in a dish.'