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. They are usually hereditary but may occur following tissue injury or trauma. Individuals who have these soft tissue tumors generally do not require treatment unless the mass causes discomfort because it compresses nerve tissue or organs. On rare occasions, they may cause hemorrhage.
Angiolipomas most commonly develop as multiple growths on the arms or chest of young adults. This type of tumor acquired the name because, in addition to fatty or adipose tissue, the mass usually contains complex vascular structures. Individuals who have these growths 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 growth is the most common and contains adipose tissue surrounded in a fibrous outer covering. These masses may be as large as a couple of inches in diameter (1 inch = 2.54 centimeters).
Fibrolipomas are a mixture of fatty and fibrous tissues. They may develop anywhere in the body but are most frequently found in and around the mouth and anywhere throughout the gastrointestinal tract. These masses often cause lymphedema and nerve compression and have been associated with hemorrhage.
The rarest form is the myelolipoma. These tumors contain fatty tissue but also consist of red and white cells as well as having platelet forming abilities, similar to bone marrow. They 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 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 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 tumor has bundles of fibrous, spindle-shaped cells and mucus material. These growths usually affect males aged 45 to 70.