Pilomatrixoma

Alternate names

Pilomatricoma; PTR; Calcifying epithelioma of Malherbe

Definition

Pilomatrixoma is a benign (non-cancerous) skin tumor of the hair follicle (structure in the skin that makes hair). They tend to develop in the head and neck area and are usually not associated with any other signs and symptoms (isolated).

Cause

• The exact underlying cause of pilomatrixoma is not well understood.
• Changes (mutations) in the CTNNB1 gene are found in at least 75% of isolated (without other signs and symptoms) pilomatrixomas.
• These mutations are somatic, which means they are not inherited and are only present in the tumor cells.
• Ihe CTNNB1 gene encodes a protein that is needed to regulate cell growth and attachment.
• When the gene is not working properly, it can result in abnormal cell growth.
• Rarely, pilomatrixomas occur in people with certain genetic syndromes such as Gardner syndrome, myotonic dystrophy, and Rubinstein-Taybi syndrome.
• In these cases, affected people usually have other characteristic features of the associated condition.

Inheritance

• Most isolated (without other signs and symptoms) pilomatrixomas are not inherited.
• However, more than one family member can rarely be affected, which suggests there may be a hereditary component in some cases.
• Rarely, pilomatrixomas occur in people with certain genetic syndromes such as Gardner syndrome, myotonic dystrophy, and Rubinstein-Taybi syndrome.
• In these cases, affected people usually have other characteristic signs and symptoms of the associated condition.
• All three of these conditions are inherited in an autosomal dominant manner.
• In some cases, an affected person inherits the mutation from an affected parent.
• Other cases may result from new (de novo) mutations in the gene.
• These cases occur in people with no history of the disorder in their family.

Signs and symptoms

• Tumors tend to develop in the head and neck area and are usually not associated with any other signs and symptoms (isolated).
• Rarely, pilomatrixomas can become cancerous (known as a pilomatrix carcinoma).
• Although they can occur in people of all ages, pilomatrixomas are most commonly diagnosed in people under age 20.

Diagnosis

• A diagnosis of pilomatrixoma is usually suspected on physical examination.
• Specialized tests may be ordered to confirm the diagnosis and rule out other conditions that cause similar features.
• These tests may include an ultrasound, an X-ray, and/or a small biopsy of the tumor.

Treatment

• Pilomatrixomas are usually surgically removed (excised).
• In most cases, the tumors do not grow back (recur) after surgery, unless the removal was incomplete.

Prognosis

• The long-term outlook (prognosis) for people with an isolated (without other signs and symptoms) pilomatrixoma is usually good.
• Most people do not experience any serious complications, although pilomatrixomas can become cancerous (known as a pilomatrix carcinoma) in rare cases.
• When surgically removed, pilomatrixomas typically do not grow back (recur), unless the excision was incomplete.
• Rarely, pilomatrixomas occur in people with certain genetic syndromes such as Gardner syndrome, myotonic dystrophy, and Rubinstein-Taybi syndrome.
• In these cases, the prognosis varies based on the condition and its associated symptoms.

NIH genetic and rare disease info

• NIH info on Pilomatrixoma

Pilomatrixoma is a rare disease.

Pilomatrixoma Resources
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