Lipoma

Lipomas (lipomata) are slow-growing, nearly always benign, adipose tumours that are most often found in the subcutaneous tissues.

They may also be found in deeper tissues such as the intermuscular septa, the abdominal organs, the oral cavity, the internal auditory canal, the cerebellopontine angle and the thorax.^1,2

Most lipomas are asymptomatic, can be diagnosed with clinical examination and do not require treatment.

• Lipomas may be seen in all age groups, but usually first appear between 40 and 60 years of age.
• Solitary lipomas are more common in women. Multiples - referred to as lipomatosis - are more common in men.
• They have an estimated annual incidence of one per 1,000 persons.³
• Congenital lipomas have been observed in children.⁴
• Lipomas have been reported that have developed following blunt trauma.⁵

Hereditary multiple lipomatosis

This is an autosomal dominant condition found most frequently in men. It is characterised by widespread symmetrical lipomas appearing most often over the extremities and trunk.

Gardner's syndrome

Lipomatosis may also be associated with Gardner's syndrome; an autosomal dominant condition involving intestinal polyposis, cysts and osteomas.

Dercum's disease

This is also known as adiposis dolorosa. It is rare and characterised by the presence of irregular painful lipomas, most often found on the trunk, shoulders, arms, forearms, and legs. It is five times more common in women and is often found in middle age. It also has asthenia and psychiatric disturbances as other prominent features.⁶

Madelung's disease

This is also known as benign symmetric lipomatosis. It is lipomatosis of the head, neck, shoulders, and proximal upper extremities. Madelung's disease, often presents in men who drink excess alcohol, who may present with the characteristic "horse collar" cervical appearance. Rarely, these patients experience swallowing difficulties, respiratory obstruction, and even sudden death.⁷

Malignancy is rare but can be found in a lesion with the clinical appearance of a lipoma. Liposarcoma presents in a fashion similar to that of a lipoma and appears to be more common in the retroperitoneum, on the shoulders and lower extremities.

Some recommend complete excision of a lipoma to exclude a possible liposarcoma, especially in fast-growing lesions.⁷
Magnetic resonance imaging has been used with some success to differentiate lipomas and liposarcomas.⁸

Tumours that have characteristics consistent with a malignant liposarcoma include those that are:³

• Greater than 5 cm in diameter
• Located on the thigh
• Deep (beneath or fixed to superficial fascia)
• Exhibiting malignant behaviour (rapid growth or invasion into nerve or bone)

• It is usually a soft or firm nodule, size 0.5 -10 cm, with smooth normal surface and skin coloured.
• While about 80% of lipomas are less than 5 cm in diameter, some can reach more than 20 cm and weigh several kg.
  
  Large lipoma on the back.
  
  
  
  
  
• They are usually situated deep in the fatty layer with normal skin overlying them and should be mobile beneath the surface.
• They are round or irregular in shape and may be single or multiple.
• Lipomas usually present as non-painful, round, mobile masses with a characteristic soft, doughy feel.
• Most lipomas are asymptomatic, but they can cause pain when they compress nerves.

This is usually made on clinical appearance alone. Any doubt should prompt referral to dermatology.

• Epidermoid cyst; these may be differentiated by the punctum in their surface and also by their site in the dermis, attached to the surface.
• Subcutaneous tumours
• Nodular fasciitis
• Liposarcoma
• Metastatic disease
• Erythema nodosum
• Nodular subcutaneous fat necrosis
• Weber-Christian panniculitis (recurring inflammation in the fat layer of the skin)
• Vasculitic nodules
• Rheumatic nodules
• Sarcoidosis
• Infections e.g. onchocerciasis
• Haematoma

• They can be left alone.
• They may need to be removed for cosmetic reasons, because of compression of surrounding structures or if the diagnosis is uncertain.
• Because lipomas generally do not infiltrate into surrounding tissue, they can be shelled out easily during excision.
• Non-excisional treatment of lipomas includes steroid injections and liposuction.⁷
• Suspicious lipomas should be evaluated radiographically, including plain films and computed tomography or magnetic resonance imaging, before excision is performed.
• Alternatively fine needle aspiration may be used to evaluate suspicious lesions.