Contributor: Gordon K. Klintworth
A lipoma is the most common benign neoplasm of soft tissue. It is impossible to distinguish a lipoma from normal adipose tissue by light microscopy. The diagnosis requires knowledge of the gross appearance of the lesion. In a adipose tissue rich structure such as the orbit a lipoma may be difficult to distinguished from an increased amount of adipose tissue or a herniation of adipose tissue. Both of the latter can cause proptosis or displacement of the eyeball. Normal orbital adipose tissue can herniate through the orbital septum. Several variants of the lipoma are recognized. They include the angiolipoma, myolipoma, spindle cell lipoma [lipoma - spindle cell], pleomorphic lipoma [lipoma - pleomorphic] and chondroid lipoma [lipoma - chondroid]. A rare congenital hamartomatous lipoma [lipoma - hamartomatous] has been documented in the orbit. A lipoma needs to be differentiated from an atypical lipoma [lipoma - atypical].