What is a pilomatricoma?

A pilomatricoma, sometimes called a pilomatrixoma, is a rare, noncancerous tumor that grows in hair follicles. It looks and feels like a hard lump on your skin. It’s most common on the head and neck, but can appear anywhere on the body. It usually affects children and young adults under the age of 20.

In very rare cases, the tumor may turn into a cancerous growth called pilomatrix carcinoma, malignant pilomatricoma, or trichomatrical carcinoma. Only 130 cases of cancerous pilomatricomas have been reported in medical literature.

What are the symptoms?

Pilomatricomas range in size from 1/4 inch to 2 inches.

pilomatricoma

A pilomatricoma is a rare, harmless hair follicle tumor that affects young children, though it can affect adults, as well. Image source: DermNet New Zealand

They tend to grow slowly and not cause any pain. In some cases, there may be more than one lump.

Other signs of a pilomatricoma include:

  • bluish-red skin
  • tent sign, which refers to the presence of angles and facets when the skin is stretched
  • teeter-totter sign, which means that pressing on one edge of the lump causes the opposite end to stick out

What causes it?

Pilomatricomas grow in the matrix cells of hair follicles. This is a collection of fast-growing cells in each hair follicle that produces hair fibers.

In cases of pilomatricoma, the hair matrix cells reproduce irregularly. Researchers aren’t sure why this happens, but it seems to be related to a mutation of the CTNNB gene, which is responsible for cells sticking together.

This mutation is acquired, meaning it’s not passed down genetically. It also shows up in both benign and cancerous pilomatricomas.

Who gets it?

Pilomatricomas primarily affect children and young adults. About 40 percent of cases happen before the age of 10, while 60 percent happen before the age of 20.

In addition, girls are about 50 percent more likely to develop a pilomatricoma than boys.

However, pilomatrix carcinomas are most common in white, middle-aged men.

How is it diagnosed?

Pilomatricomas are frequently confused with other benign skin growths, such as dermoid or epidermoid cysts. To confirm that a growth is a pilomatricoma, your doctor may do a skin biopsy. This involves removing all or part of the lump and looking at the tissue under a microscope. This will also show whether the spot is cancerous.

How is it treated?

Pilomatricomas generally don’t cause any problems, but they also don’t go away. They can also become quite large over time, so people often prefer to have them removed.

If you want to have a pilomatricoma removed, your doctor will likely recommend surgical excision, which involves cutting out the tumor. This is a fairly straightforward procedure that can often be done using local anesthesia. Once your doctor has removed the tumor, they might run some tests on it to confirm that it’s not cancerous.

Are there any complications?

A very small number of pilomatricoma tumors may become cancerous. However, only about 90 cases of this have been reported since 1980.

If a biopsy shows that your pilomatricoma is cancerous, your doctor will remove it, along with some of the surrounding skin. This decreases the risk that it will grow back in the future.

What’s the outlook?

A pilomatricoma is a rare but usually harmless skin tumor that mostly affects children and young adults. While pilomatricoma tumors usually don’t cause any problems, your doctor might recommend surgical removal to prevent them from getting larger over time.