Scientists typically name different types of lipomas for the location in which they develop. The benign tumors contain fatty tissue that may accompany collagen, or other fibrous tissue, and vascular structures. Lipomas are usually hereditary but may occur following tissue injury or trauma. Individuals having these soft tissue tumors generally do not require treatment unless the mass causes discomfort from compression of nerve tissue or other organs. On rare occasions, lipomas may cause hemorrhage.

Angiolipomas most commonly develop as multiple growths on the arms or chest of young adults. This type of lipoma acquired the name because, in addition to fatty or adipose tissue, the mass usually contains complex vascular structures. Individuals having angiolipomas usually complain of discomfort.

Conventional lipomas form beneath the skin. The mass is generally painless and movable beneath the skin’s surface. This type of lipoma is the most common and contains adipose tissue encapsulated in a fibrous outer covering. These masses range in size from a couple of centimeters to a couple of inches in diameter (1 inch = 2.54 centimeters).

Fibrolipomas are a mixture of fatty and fibrous tissues. These masses may develop anywhere in the body but are most frequently found in and around the mouth and anywhere throughout the gastrointestinal tract. These lipomas often cause lymphedema and nerve compression and have been associated with hemorrhage.

The rarest form of lipoma is the myelolipoma. These turmors contain fatty tissue but also consist of red and white cells as well as having platelet forming abilities, similar to bone marrow. These lipomas usually develop singly on the inside or exterior of an adrenal gland. Myelolipomas most often affect men from the ages of 40 to 60. Individuals having this type of lipoma may experience bloody urine, hypertension, and pain from organ compression.

Pleomorphic lipomas usually appear on the back of the neck, the upper back and shoulders. Unlike typical lipoma growths, these masses vary in fat content, which may range anywhere from 10% to 90%. Accompanying the fat tissue, are bundles of collagen fibers, blood vessels, and empty spaces.

Spindle cell lipomas are frequently mistaken for a malignancy known as liposarcoma. These growths are generally firmer to the touch than average lipoma masses. They contain gray, white and yellow coloration. Besides fatty tissue, the spindle cell has bundles of fibrous spindle shaped cells and mucus material. These growths usually affect males aged 45 to 70.