Lipoma and Atheroma: How to Tell Them Apart and How Doctors Distinguish Them

You have found a lump under your skin and do not understand what it is. Most often it is a lipoma or an atheroma — two different formations that are easy to confuse by touch. We will explain how they differ and how a doctor distinguishes them during an appointment.

What a lipoma is and what an atheroma is

A lipoma is a soft lump of fat under the skin. It is harmless, usually does not hurt, and grows slowly. Its size ranges from a pea to several centimeters. Lipomas often appear on the shoulders, chest, arms, back, buttocks, and thighs, but they can also occur on the forehead.

An atheroma is a sebaceous gland cyst that arises because its duct becomes blocked. It appears where hair grows: on the scalp, face (especially below the mouth), back, neck, and in the genital area. An atheroma is often called a sebaceous gland cyst, although by the composition of its contents it is an epidermoid cyst: it is filled with keratinized skin cells, whereas a true sebaceous cyst contains a yellowish oily substance.

How a lipoma differs from an atheroma: appearance and location

A lipoma feels soft and shifts slightly under the skin when pressed.

An atheroma is a firm-elastic formation with clear contours, mobile. The skin over it cannot be gathered into a fold. Often a tiny dot or dimple is visible in the center. If the atheroma becomes inflamed, pain, redness, swelling, and fever appear. Sometimes it ruptures on its own: pus with a sebaceous content is discharged.

Has the atheroma become inflamed: how to distinguish it from other formations

An atheroma remains painless for a long time. If it becomes inflamed, pain, redness, swelling, fever, and fluctuation appear. Inflammation may be a sign of a suppurating atheroma, but distinguishing it from other formations by appearance alone is difficult — this is decided by a doctor.

What ultrasound shows in lipoma and atheroma

A doctor can usually identify a lipoma on examination. If there are doubts, the doctor may refer you for ultrasound or another scan to clarify the nature of the formation. If infection is suspected, a culture of the contents may be needed.

When a biopsy is ordered

Sometimes a biopsy is needed to rule out other conditions. If the formation is removed, the tissue may be sent to a laboratory to confirm that it is a lipoma. This is necessary because some types of skin cancer look like cystic nodules.

When to see a surgeon

You should see a doctor if any new lump appears. Especially if it hurts, is red or hot to the touch, is hard and immobile, or is increasing in size. Lipomas and atheromas are usually not dangerous and do not require removal if they are not growing and do not cause discomfort. Lipomas are removed if they grow or cause symptoms because of their location; an atheroma may return if it is not completely removed. Ask the surgeon questions: what is the nature of the formation, is observation needed, and what examinations does he recommend.

• The lump has appeared for the first time or has changed
• The formation hurts, is red, or is hot
• It is hard and does not shift under the skin
• The formation is rapidly increasing in size
• Contents are discharged from it

A subcutaneous lump by itself is not a reason to call an ambulance. 103/112 — for life-threatening situations, for example, a sharp deterioration in general condition.

This material is for reference and does not replace a doctor's consultation: the final diagnosis is made by a specialist after examination.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer