A lipoma is a benign tumor composed of mature adipose tissue. It is the most frequently occurring benign soft tissue tumor and is often asymptomatic.
Superficial lipomas predominate in women, whereas deep lipomas are more common in men. The peak incidence of lipomas occurs between 40 and 60 years of age.
Superficial lipomas are usually localized to the subcutaneous tissue of the trunk and proximal extremities. Deep lipomas are usually in the retroperitoneum, chest wall, and deep soft tissue of the hands and feet.
On CT scans, lipomas have a low attenuation coefficient, equal to that of subcutaneous fat, and they do not enhance after administration of contrast material.
On MR images, they have the same signal intensity characteristics as subcutaneous fat on all imaging sequences.
On both CT and MR images, lipomas have a homogeneous appearance, although occasional thin fibrous septa can be present.