|Classification and external resources|
Accessory breasts, also known as polymastia, supernumerary breasts, multiple breast syndrome, or mammae erraticae, is the condition of having an additional breast. Extra breasts may appear with or without nipples or areolae. It is a condition and a form of atavism which is most prevalent in male humans, and often goes untreated as it is mostly harmless. In recent years, many affected women have had a plastic surgery operation to remove the additional breasts, for purely aesthetic reasons.
A related condition, in which extra nipples form, is called "supernumerary nipple" or "polythelia".
In some cases, the accessory breast may not be visible at the surface. In these cases, it may be possible to distinguish their appearance from normal breast tissue with MRI. In other cases, accessory breasts have been known to lactate, as illustrated in a woodcut showing a child nursing at ectopic breast tissue on the lateral thigh.
In fiction 
Some science fiction and comedy films have featured minor female characters with one or more additional breasts: The Warrior and the Sorceress (four breasts); Total Recall (three breasts); Star Trek V (three breasts); Earth Girls Are Easy (four breasts); Firecracker (three breasts); Flesh Gordon 2 (more than four breasts, but just on a sign); Good Luck Chuck (three breasts); Dumb and Dumberer (three breasts); Silence of the Hams (three breasts); Necropolis (six breasts); Paul (three breasts); and Return of the Jedi (six breasts)(the Askajian).
The Hitchhiker's Guide to the Galaxy series features many references to "Eccentrica Gallumbits, the triple-breasted whore of Eroticon Six".
- Laor T, Collins MH, Emery KH, Donnelly LF, Bove KE, Ballard ET (2004). "MRI appearance of accessory breast tissue: a diagnostic consideration for an axillary mass in a peripubertal or pubertal girl". AJR Am J Roentgenol 183 (6): 1779–81. PMID 15547228.
- "Supernumerary Breast Tissue". Southern Medical Journal. Retrieved Dec. 30, 2008.
- Emsen IM (2006). "Treatment with ultrasound-assisted liposuction of accessory axillary breast tissues". Aesthetic Plast Surg 30 (2): 251–2. doi:10.1007/s00266-005-0160-7. PMID 16547633.
- A Paper on the Appearance of Multiple Mammaries in Humans, R. Eghardt, Oxford University Press (1923)
- Weird Diseases, B. Hargreaves and M. Wallette, Emu Publishing (2007)
- Cases of suckling from extra breasts
- Old woodcut of extra breast in use
- An example of multiple breast syndrome (Norwegian)
- An example of multiple breast syndrome (English)