Stevie C sent along this article on
An unusual presentation of supernumerary breast tissue (just what were you googling for, Stevie?), in which a woman reports an annoying growth on her foot, and when examined, is discovered to have a breast growing there, complete with nipple and fatty tissue (but in this case, no glandular tissue).
It’s in the Dermatology Online Journal, not the Onion.
I hadn’t heard of this before myself, but it’s fascinating. 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. I’d love to know what the molecular signal for initiating differentiation—I suspect it’s something simple and common.