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- Discussion:
    - benign tumor composed of lobules of mature fat;
    - most common tumor of soft tissue;
    - occurs most often in adults;
    - tumor usually presents as active stage 2 lesion, later becoming latent;
    - usually it appears as soft, slowly enlarging, asymptomatic mass located superficially in subQ tissues, commonly seen in the back, buttocks, and thighs;
    - it can also appear deep to the fascia, lying in fatty planes along N/V bundles;
           - lipomas do not cross fascial boundries but will grow in between fascial planes;
           - lipomas that arise in deep tissues may become remarkably large;
           - these lesions may have a firm consistency similar to a sarcoma; 
    - diff dx: liposarcoma: most occur proximal to the knee and elbow; 
    - sub-types:
           - intra-muscular lipoma:
                  - these lesions can become large in size before detection;
                  - typically has a firm consistency which mimics sarcoma;
                  - often these lesions will be in close contact w/ neurovascular bundle;
           - angiolipoma:
                  - variant of lipoma w/ vascular component, occurs in children as a deep, subcutaneous or intramuscular soft mass;
                  - it is distinguished from ordinary lipoma by distinct tenderness to palpation;
                  - angiography is the best method for diagnosing angiolipoma;
                  - note that in the majority of cases multiple tumors may be present;
                  - diff dx:
                         - Kaposi's sarcoma;
                         - angiosarcoma
           - spindle cell sarcoma:
                  - presents as a painless nodule;
                  - histologically the tumor contains a mixture of fat and spindle cells

- Radiographic studies:
    - crisply marginated radiolucent image;
    - may show calcification in areas of necrosis and metaplastic bone or cartilage;

- MRI:
    - w/ lipoma, signal intensity of lesion parallels that of subcutaneous fat on all pulse sequences (T1 and T2);


- Bone Scan:
    - usual avascular lipoma appears avascular on bone scan;
    - if bone scan is hot consider liposarcoma;

- Treatment:
    - marginal excision is successful for lipoma, and recurrences are rare;
    - note that lipomas cannot be read by frozen section, and can only be interpreted by permanent sections

Suspected adipose tumours of the hand and the potential risk for malignant transformation to sarcoma: a series of 14 patients

Intraosseous lipomas. A clinicopathologic study of 66 cases.

Size, site and clinical incidence of lipoma. Factors in the differential diagnosis of lipoma and sarcoma.

A 20-year retrospective review of surgically treated liposarcoma at the Cleveland Clinic.

Atypical Lipomatous Tumors/Well-differentiated Liposarcomas: Clinical Outcome of 67 Patients