Lipoma
KEY FACTS
Imaging
Diagnostic Checklist
Large size, deep location, and heterogeneity are best indicators of liposarcoma
However, not all heterogeneity within lipoma indicates liposarcoma
Calcification, small nonfatty areas, myxoid tissue, and fat necrosis can be features of atypical lipoma and lipoma variant but are not necessarily diagnostic of liposarcoma
TERMINOLOGY
Synonyms
Definitions
Lipoma: Benign soft tissue tumor composed of mature adipose tissue
Angiolipoma: Lipoma in which small capillary-sized vessels containing microthrombi transverse tumor
Lipomatosis: Diffuse infiltrative overgrowth of mature adipose tissue, completely or partially encapsulated
Lipomatosis of nerve: Median > > > other nerves ± localized mesenchymal overgrowth
Spindle cell lipoma: Mixture of fat and spindle cells; more common in head and neck subcutaneous tissues and adult males
Lipoblastoma: Admixture of mature and immature adipocytes; more common in extremities and children < 3 years old
Hibernoma: Tumor of brown (thermogenic) fat similar to that found in hibernating animals; > subcutaneous tissues of adults, especially lower neck, mediastinum, and upper dorsal region
Chondroid lipoma: Adult females, shoulder or pelvic girdle, may calcify
Myolipoma: Benign tumor exhibiting features of mature smooth muscles and mature adipose tissue
Lipoma arborescens: Subsynovial fatty proliferation, knee > > > ankle or hip; may occur in tendon sheath
Dedifferentiated liposarcoma: Deep-seated and large with significant (> 25%) nonfatty component; malignant potential
Myxoid liposarcoma: Myxoid tumor either low grade (< 5% round cell component) or high grade (> 5% round cell component)
Pleomorphic liposarcoma: Large mass with myxoid, necrotic, fatty, and hemorrhagic components
IMAGING
General Features
Ultrasonographic Findings
Variable echogenicity depending on cellularity and fat-water content
Well-defined, encapsulated mass, usually iso- to slightly hyperechoic to adjacent fat
Distinctive, fine linear striations parallel to skin
Typically fusiform or oblong in shape
Encapsulated
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on the anterior aspect of the proximal arm.
causing focal contour bulging of the skin. The lipoma contains fine linear striation parallel to the skin. The underlying deltoid muscle is normal 
.
. The fine striations are barely perceivable, though these appearances are still characteristic of a lipoma. Such lipomas are often multiple and tend to be located more centrally than peripherally.
and the fine linear horizontal striations 
.
