dome- or egg-shaped and typically measure 2 to 10 cm in diameter. They most commonly appear on the shoulders, neck, trunk, and arms, although they may appear in any part of the body that possesses fatty tissue (Figure 6.4.1). Angiolipomas differ in that they may be painful or tender. Lipomas are usually superficial but may be deep but are not attached to underlying structures (Table 6.4.1). Lipomas may be intramuscular. When present inside an organ, such as muscle, the mass will be difficult to palpate and should be examined by computerized tomography (CT) and/or magnetic resonance imaging (MRI) (Figure 6.4.2). Lipomas have been
rarely found in many visceral, thoracic organs, as well as in the central and peripheral nervous systems and genitourinary organs (summarized in Table 6.4.2). A soft to firm nodule may represent the rare variant of fibrolipoma characteristic of Dercum disease (Figure 6.4.3A).
TABLE 6.4.1 Lipoma Subtypes
FIGURE 6.4.2 Computed tomography (A) and surgical (B) images of intramuscular lipoma. White arrows highlight the borders of the lipoma within the muscle.
TABLE 6.4.2 Lipomas Arising in Organs
area that alerts the patient to a mass. When the tumor is larger and invades neighboring structures there may be tenderness, pain, numbness, fatigue, or functional disturbances. Liposarcomas in the retroperitoneal area are usually quite large before diagnosis is established.5
TABLE 6.4.3 Lipomatosis Syndromes