Lipomas Workup

Updated: Jun 08, 2017
  • Author: Todd A Nickloes, DO, FACOS; Chief Editor: John Geibel, MD, DSc, MSc, AGAF  more...
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Workup

Laboratory Studies

A study by Yoshiyama et al suggested that the plasma D-dimer level could contribute to the differentiation between lipoma and well-differentiated liposarcoma, two lesions that are similar in terms of clinical, radiologic, and pathologic characteristics. [13]

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Imaging Studies

For most subcutaneous lipomas, no imaging studies are required.

Lesions in the gastrointestinal (GI) tract may be visible on GI contrast studies (see the image below).

Upper gastrointestinal series shows duodenal lipom Upper gastrointestinal series shows duodenal lipoma with central ulceration where the overlying mucosa has thinned, ulcerated, and bled.

Imaging studies for lipomas in atypical locations (or those for which the differential diagnosis includes sarcoma) include ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI). [14]

In a retrospective review of the use of ultrasonography by two musculoskeletal radiologists to evaluate 714 superficial soft-tissue tumors, Hung et al reported a sensitivity of 95.2% and a specificity of 94.3% for lipoma. [15]

When CT is employed, a radiodensity of less than 50 Hounsfield units is indicative of a soft-tissue tumor composed of fat, though no reliable distinction can be made between a benign lipoma and a malignant liposarcoma. [6]

MRI has been recommended as a reliable preoperative investigation. [16, 17, 18, 19, 6] It has been employed in intramuscular lipoma, pediatric lipoblastomas, and others. The findings of intramuscular lipomas, for example, range from small, homogeneous masses to large, inhomogeneous lesions with infiltrative margins. However, like CT, MRI does not allow an absolute, reliable distinction between a lipoma and a liposarcoma. [20]  A study by Thornhill suggested that the addition of computer-assisted diagnosis may improve the ability of MRI to make this distinction. [21]

Because all lipomas are radiolucent, soft-tissue radiography can be diagnostic, but it is indicated only when the diagnosis is in doubt.

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Biopsy

Biopsies are normally not indicated for small subcutaneous lesions, because the entire tumor is usually removed. All imaging techniques have been combined with fine-needle aspiration (FNA); this combination increases the accuracy of diagnosis. Obtaining tissue samples from different tumor components is important, because it provides samples for histopathologic analysis by means of various techniques, including fluorescence in situ hybridization (FISH).

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Histologic Findings

Lipomas are benign mesenchymal tumors derived from adipocytes. Several variants have been described, including the following:

  • Adenolipomas, a variation of lipomas that may occur in the breast, often have a marked fibrotic component; they are best regarded as a hamartoma
  • Angiolipomas contain many small vessels
  • Cardiac lipomas may calcify following fat necrosis; microscopically, they are composed of fatty tissue with interlacing muscle fibers

FNA biopsies of a lipoblastoma contain multivacuolated lipoblasts, myxoid areas, and a plexiform capillary network.

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