This article waslast modified on July 10, 2017.

1) The most common use of the term refers to a bone disorder in which bone is formed and broken down excessively, resulting in weakened bones. This condition can cause bone pain, deformed bones, arthritis, and numerous fractures.

2) Other, less common uses of the term refer to rare forms of cancer involving the nipple of the breast or the skin of other areas such as the perianal region, penis, or vulva (also termed extramammary).