Cutaneous Lipomas

Background

Lipomas are benign tumors composed of mature fat cells. They are the most common benign mesenchymal tumor. Lipomas are found in the subcutaneous tissues and, less commonly, in internal organs. Most cases are easy to diagnose and do not affect morbidity. Lipomas typically develop as discrete rubbery masses in the subcutaneous tissues of the trunk or proximal extremity. Lipomas are usually a few centimeters in size and can be removed by surgical excision or, less commonly, liposuction. Also see the Medscape Drugs & Diseases general surgery article, Lipomas.

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Pathophysiology

Lipomas differ biochemically from normal fat by demonstrating increased levels of lipoprotein lipase and the presence of a large number of precursor cells.

Approximately 60% of solitary cutaneous lipomas display clonal alterations. The most common alteration involves a breakpoint on bands 12q13-15. Karyotype aberrations also have been noted on arms 6p and 13q. Multiple lipomas do not display these alterations.^[1]

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Epidemiology

Frequency

In one study of a Scandinavian population, 43% of benign mesenchymal tumors were lipomas. Overall, the incidence of a lipoma occurs in 1 in 1000 people.^[2]

Sex

Solitary lipomas are seen predominately in women. Multiple lipomas occur more frequently in men.

Age

Lipomas can occur at any age; however, they usually arise in early adulthood. Rarely, they can occur in childhood or infancy.^[3]

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Prognosis

Cutaneous lipomas can cause mild tenderness, and angiolipomas are often tender. Lipomas are not associated with fatalities.

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History

Patients report a slowly growing lesion present for several years and usually do not complain of discomfort. Lipomas are classified in the categories described below.

Solitary lipomas (most common)

Most solitary lipomas are superficial and small. Solitary lipomas may develop with weight gain but usually do not shrink after weight loss.

Diffuse congenital lipomatosis

Diffuse, poorly demarcated lipomas localized primarily on the trunk characterize this type, as shown in the image below.

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A 43-year-old white man with a 3- to 4-year history of a slow-growing asymptomatic growth on his right shoulder.

Tumors often infiltrate through muscle fibers, making them resistant to surgical excision. These tumors are composed of immature fat cells.

Benign symmetric lipomatosis (Madelung disease) ^{[4, 5, 6]}

Madelung described the condition in 1888. Lipomas of the head, neck, shoulders, and proximal upper extremities characterize this condition. Men are affected 4 times as often as women. The patient's history often includes excessive alcohol consumption or diabetes.

Other conditions associated with Madelung disease include malignant tumors of the upper airways, hyperuricemia, obesity, renal tubular acidosis, peripheral neuropathy, and liver disease.

Familial multiple lipomatosis

This clinical entity is characterized by few-to-many, small, well-demarcated, encapsulated lipomas that commonly involve the extremities. Typically, this form appears during or soon after adolescence. The neck and shoulders usually are spared (unlike benign symmetric lipomatosis). A family history of multiple lipomas usually exists, and an autosomal dominant mode of inheritance is expressed.

Dercum disease (adiposis dolorosa) ^{[7, 8, 9, 10]}

Painful lipomas are the hallmark of this rare condition. Lipomas typically occur on the extremities of obese postmenopausal women. Alcoholism, emotional instability, and depression are commonly associated.

Angiolipomas

These tender, soft, subcutaneous nodules are present in adolescence. These are lipomas that have a vascular component. Tumors frequently are multilobulated and firmer than ordinary lipomas. The associated pain is vague and may be spontaneous or caused by external pressure.

Hibernomas

Tumors are solitary well-circumscribed nodules that are asymptomatic. They are located in the interscapular region, axillae, neck, or mediastinum. Histologically, hibernomas are composed of embryonic brown lipoblasts that are termed mulberry cells because of their appearance on pathology.

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Physical Examination

Lipomas present as subcutaneous nodules ranging from 2 cm to greater than 10 cm. There are cases of lipomas growing to very large sizes (over 30 cm) and causing discomfort and distortion to the body part involved; however, this is very rare. Lipomas feel soft and rubbery and are often multilobulated. Skin overlying the lesion is normal and not connected to the tumor. The neck, back, and proximal extremities are most commonly affected.

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Imaging Studies

CT scanning is indicated in a suspected liposarcoma. CT scanning is useful for distinguishing between lipomas and liposarcomas.^[14]

Ultrasonography can be a useful modality for the diagnosis of lipomas. Compared with palpation, diagnostic accuracy rates were 88.1% with ultrasonography versus 54.8% with palpation alone (P< .01).^[15]

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Procedures

Fine-needle aspiration or biopsy is indicated when the diagnosis of liposarcoma is suspected.

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Histologic Findings

Lipomas histologically resemble normal fat. When completely excised, a thin fibrous capsule surrounding the aggregate of adipocytes may be seen. Without a clinical or gross description, it can be impossible to distinguish between tumor cells and mature adipocytes.

One report describes the diagnostic challenge when encountering low-fat or fat-free pleomorphic lipomas. The authors suggested that identifying the classic nonlipogenic components and considering the clinical context are essential to ensuring diagnostic accuracy in pleomorphic lipomas.^[16]

Lipomas differ biochemically from normal mature fat. Lipomas have increased levels of lipoprotein lipase.

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Medical Care

When asymptomatic, lipomas can be left alone. When treatment is considered, surgical excision is the preferred treatment. In Dercum disease, medical treatment can be offered using steroids and analgesic medications.^[17] Topical EMLA (eutectic mixture of lidocaine and prilocaine in a ratio of 1:1 by weight) also has been used for Dercum disease.^[18] In a case report of two patients with Dercum disease and chronic hepatitis, interferon alfa-2b induced long-term pain relief.^[19]

Mesotherapy^{[20, 21]} is a treatment for body contouring that has been used for many years in Europe. Mesotherapy involves a series of injections containing many different ingredients, including vasodilators, nonsteroidal anti-inflammatory drugs, enzymes, and hormones. A common chemical used is lecithin (phosphatidylcholine isoproterenol), a lipolytic agent. However, one study showed that when lecithin solubilized with deoxycholate and was used to treat subcutaneous lipomas, the active ingredient was actually the deoxycholate rather than the phosphatidalcholine.^{[22, 23]} This study suggested that low concentrations of deoxycholate may be a safe and effective treatment for small collections of fat.

A product manufactured in Europe uses a fat-dissolving injectable to treat lipomas. In 2018, a Polish study showed that Aqualyx (12alfa-dihydroxy-5beta-24-oico cholanic acid sodium salt) dissolved 70% of treated lipomas. The procedure was performed under ultrasound guidance. This is a form of injection lipolysis referred to as lipotherapy or intralipotherapy.^[24]

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Surgical Care

Multiple surgical techniques can be used in treating lipomas. It is important to evaluate infiltrating lipomas carefully when considering excision, since they can develop in intramuscular or intermuscular locations. They also can infiltrate into tendon, bone, and nerve tissue, thus requiring careful microdissection to preserve important structures.^{[25, 26, 27]}

Simple surgical excision of lipomas

Mark the palpable borders on the skin before injecting with local anesthesia, as shown in the image below.

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A 43-year-old man with a slow-growing asymptomatic growth.

Incise skin down to the lipoma capsule and dissect to free the mass from the surrounding tissue.

After obtaining hemostasis, close the dead space using buried absorbable sutures. Remove excess skin, close the wound, and apply a pressure dressing for 24 hours to prevent hematoma or seroma formation.

Squeeze technique (for small, superficial lipomas)

Make a stab incision, which can be as small as one-fourth of the lipoma's diameter. Express the lipoma by putting pressure on the lateral aspects of the incision, as shown in the image below.

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Surgical excision of a 6-cm lipoma on the back of a 54-year-old man using the squeeze technique.

Gentle dissection with a curette or blunt undermining may be required.

Liposuction for lipomas ^{[28, 29, 30, 26]}

Liposuction has been shown to be an excellent method for removing lipomas, angiolipomas, the lipomas of Madelung disease, and adiposis dolorosa. The advantages of liposuction include reduced operative time and smaller incisions.

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