Lipoma

1368

Benign fatty tumor that is the most common soft tissue tumor in adulthood.

Subclssified as lipoma, angiolipoma, fibrolipoma, myelolipoma, pleomorphic, and spindle cell types.

Compose of a collection of mature normal adipocytes arranged in lobules and enclosed by a well defined thin fibrous capsule.

The most common mesenchymal neoplasm.

Sites primarily include: the back, shoulders, and proximal portion of the extremities, abdomen, buttocks, and posterior neck.

Most lesions are asymptomatic and solitary.

Most are less than 1cm in diameter.

Typically mobile and non tender.

Most common benign soft tissue mesenchymal tumors.

It is multiple in approximately five percent of cases.

Etiology is unknown.

Fibrous septa rupture after trauma accompanying a tear in the anchorage may result in adipose tissue prolfiferation and the induction of cytokne release that may trigger adipocyte differentiation and maturation.

Formed of adipose tissue.

Genetic predisposition and clonal chromosomal aberrations are common.

Rarely, especially when multiple ay be associated with Gardner syndrome, Cowden syndrome, Proteus syndrome, Bannayan-Riley-Ruvalcaba syndrome, Pai syndrome, benign symmetric lipomatosis, adiposis Dolorosa, congenital lipomatosis, and hereditary multiple lipomatosis.

Can occur in all organs, but most commonly in the subcutaneous tissue.

If close to vital tissues, can mimic a variety of conditions.

Estimated to occur in 0.2% to 1% of the adult population.

Prevalence of approximately 1%.

Peak incidence 40-60 years of age, but young adults and children can be affected.

May show rearrangements of 12q14-15, 6p, and 13q.

Spindle cell and pleomorphic lipomas may have rearrangements of 16q and 13q.

Most common type is well encapsulated mass of mature adipocyte cells that vary in size.

Infrequently lesions may be large, intramuscularly and poorly defined.

This size usually is from 2-5 cm in diameter, and rarely greater than 10 centimeters.

Soft, mobile and painless.

Usually presents as a slow growing, soft, well-circumscribed, rounds or oval, lobulated, dome-shaped or egg-shapedmass, not attached to overlying skin or underlying structures.

Solitary lipomas are more common in females, where as multiple lesions are more common in males.

Overlying skin is usually normal.

Lesions are usually sporadic, although familial cases have been reported.

More common in the obese.

Diagnosis is primarily clinical.

No imaging studies are necessary and plain radiographs usually demonstrate lucencies in the soft tissue consistent with fat.

In very large lesions ultrasound, CT or MRI imaging may be considered especially if they have atypical features or appear deep.

Biopsy can be performed if the diagnosis is in doubt.

Differential diagnosis includes: liposarcomas, epidermoid cyst, dermatofibroma, angiolipoma, hematoma, abscess, keloid, panniculitis, neurofibroma, ganglion, rheumatoid nodules, and metastases.

Rarely when in other locations may cause pain, breathing difficulties, arrhythmias, dysphagia, or intestinal obstruction.

Malignant transformation is rare.

Usually cured by simple excision.