Xanthoma

What is a xanthoma?

A xanthoma (pronounced “zan-thoma”) is a non-cancerous growth made up of immune cells called histiocytes. Histiocytes are specialized cells that help remove waste products from the body. The histiocytes in a xanthoma look much larger than normal histiocytes because they are full of lipids (fat).

Where are xanthomas normally found?

Xanthomas can develop anywhere in the body but they are most commonly found in the skin, stomach, colon, and bladder. In the skin or around joints, xanthomas appear as yellow bumps.

What causes a xanthoma?

Xanthomas that arise in the skin are often associated with high blood cholesterol levels. For this reason, these growths are common in patients who have diabetes or other genetic conditions that lead to high blood cholesterol levels. Treatment that leads to lowered blood cholesterol levels can cause the xanthomas to shrink or even disappear.

Types of xanthomas

Doctors divide xanthomas into types based on their location and clinical features. The following is a list of the most common types.

  • Xanthelasma: Xanthelasma is the most common type of xanthoma. It typically develops on the skin of the eyelid.
  • Palmar xanthoma: This type of xanthomas develops on the palms of the hands.
  • Tuberous xanthoma: This type of xanthoma appears as a firm bump, typically on the knees or elbows.
  • Tendon xanthoma: This type usually develops on the Achilles tendon of the heel or on the tendons of the fingers.
  • Eruptive xanthoma: This type of xanthoma appears as multiple small bumps that are often itchy.
  • Verruciform xanthoma: This type of xanthoma is called “verruciform” because when examined under the microscope, it resembles another type of non-cancerous growth called verruca vulgaris.

How do pathologists make this diagnosis?

When they arise on the skin, the diagnosis is usually made after the xanthoma has been removed and sent to a pathologist to examine under the microscope. In other parts of the body, such as the stomach or bladder, the diagnosis is usually made when a tissue sample is examined for another reason.

When examined under the microscope a xanthoma is made up of many lipid-filled (fat-filled) histocytes. Pathologists sometimes describe these cells as foamy histiocytes because the inside of the cell looks like it is filled with a clear foam.

xanthoma

The diagnosis of xanthoma is important because it may be the first clue that a patient has high blood cholesterol levels. If you have been diagnosed with xanthoma, please talk with your doctor to see if additional tests for blood cholesterol are appropriate for you.

by Robyn Ndikumana MD FRCPC (updated June 15, 2021)
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