Lipomas

Lipomas are noncancerous slow growing tumours composed of mature fat cells.[1]  They may appear in various parts of the body including the breast.

They tend to feel spongy, smooth and are moveable.  Lipomas in the breast vary in size, and cause no discomfort.  Their size will not decrease with weight loss.

The cause of lipomas is unknown. 

A fine needle aspiration, core biopsy, or surgical excision can be done to confirm the diagnosis of a lipoma.  When removed, they resemble fat, feel rubbery and a thin fibrous capsule may be seen around the entire lump (encapsulated).  Since the tumour is benign, they do not require further treatment.[2]

[1] Lipomas.  eMedicine.  Retrieved December 20, 2005 , from http://www.emedicine.com/DERM/topic242.htm