Just a week or so ago I was speaking to a physician friend of mine who was telling me about patients with breast tissue growing at odd parts of their bodies.  I thought "huh, that’s weird, never heard of anything like that before".  I guess a breast always seemed to me such a complex organ that it couldn’t just randomly pop out just anywhere.  As if on cue, Pharyngula links to a paper about a woman with a breast on her foot:

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….Supernumerary nipples, and less frequently supernumerary breasts, are present in about 1-5 percent of the population [1].
Such alterations are more common in women, usually occurring along the
embryonic milk line, which extends from the axilla to the groin [1, 2].
Supernumerary breast tissue (SBT) is rarely found beyond the mammary line…

Putting aside the thought of how strange it must be to walk on that thing, I wonder if, as PZ Myers suggests, it would be relatively easy to grow a breast in vitro, and does this have implications for reconstructing breasts post-mastectomy.