Lipoma

A lipoma is a common benign tumour of adipose tissue. Lipomas are usually found in the subcutaneous tissue and less commonly in internal organs. Lesions are solitary or multiple and usually of no significance, however, they can be associated with neurofibromatosis and rarely a number of other syndromes.

This chapter is set out as follows:

• Lipomas can occur at any age, however, they tend to arise in adulthood
• Solitary lipomas are more common in women whilst multiple lipomas occur more frequently in men
• Lesions are often asymptomatic unless large in which case they can cause pain through pressure on various structures

Distribution

• May be solitary, multiple, sometimes very numerous
• The arms, back of the neck, trunk and thighs are the most common sites

Morphology

• A subcutaneous nodule, often lobulated, with a soft doughy consistency
• The overlying skin surface is normal and freely mobile over the lipoma
• Lesions are often 2-10 cm in diameter but can be much larger

Differential diagnosis

Lipomas are usually easy to tell apart from epidermoid cysts, which are firm and often have a central punctum. Other conditions to be aware of include:

• Angiolipomas: account for about 10% of all lipomatous lesions. They are morphologically similar to lipomas but can be intermittently painful or tender. They differ histologically by having excessive degrees of capillary proliferation

• Lipomatosis: this term encompasses a spectrum of rare disorders characterised by the diffuse infiltration of structures with non-encapsulated adipose tissue. One such condition is multiple symmetrical lipomatosis, which has neck and mediastinal involvement along with neuropathic changes

• Dercum's disease (syn. adiposis dolorosa): a rare syndrome characterised by deposits of tender adipose tissue, ecchymoses and obesity, typically in middle aged women

• Cutaneous sarcomas: there are many different types of sarcoma. Deep-seated lesions are likely to grow much more quickly than lipomas, become painful and may be associated with a bruise-like skin discoloration. Refer to the chapter Liposarcoma

• Most lipomas require no treatment

• Surgical excision can be used for symptomatic lesions, or enlarging lesions on sites that are likely to become symptomatic

• Lipomas may be significantly larger than they appear on clinical examination - the excision of lipomas should only be undertaken by health professionals who have had the appropriate training in skin surgery and understand the anatomy of where the lipoma is found and are able to use surgical techniques that close the dead space following the removal of the lipoma

• Frontal lipomas: are found on the forehead and are often mistaken for epidermoid cysts. They arise from within the frontalis muscle or from deeper structures, are more complicated to manage and so must be excised only by health professionals trained to a high standard of skin surgery 

• Liposarcomas: any atypical lesion (history and / or examination) should be considered for an urgent referral (two-week wait)

• The following link provides a video clip showing the removal of a lipoma