Diagnosing Birthmarks in Children

NYU Langone dermatologists can usually diagnose the type of birthmark on your child’s skin based on a visual examination. If they need more information about the nature or type of birthmark, or if a birthmark or pattern of birthmarks suggests another medical condition, they may recommend additional testing.

Medical History

When meeting with our dermatologists, you may be asked for details about whether members of your family have birthmarks or other medical conditions that are sometimes associated with birthmarks, such as skin cancer.

This information helps doctors assess the need for additional testing. For example, if your child has several café-au-lait spots on the skin and someone in your family has neurofibromatosis type 1, doctors may be more likely to recommend that your child be tested for this condition.

Our dermatologists may also ask whether any birthmarks have changed in size, color, shape, or texture. Some birthmarks, such as hemangiomas, grow very rapidly and can double or triple in size within weeks. Many other types of birthmarks don’t grow or change shape at all. Our doctors closely monitor any birthmark that is rapidly changing.

Physical Exam

A physical exam performed by our dermatologists involves a close examination of your child’s skin from head to toe. Doctors look for patterns that may suggest any associated medical condition. Our doctors also pay close attention to birthmarks that are located on sensitive areas—such as the lips, mouth, and eyes—because they may have an impact on functional development.


Ultrasound is a painless, noninvasive imaging test that uses high-frequency sound waves to produce images of structures inside the body.

If a dermatologist examines a birthmark or group of birthmarks and determines that more information is needed to make a diagnosis, he or she may order an ultrasound. Performed by our radiologists, an ultrasound can show how far below the surface of the skin a birthmark reaches and whether other parts of the body may be involved.

Doctors also use ultrasound to look for birthmarks that may have developed internally and determine whether they pose a health risk. For example, if a cluster of small hemangioma birthmarks appears on a child’s face, this may be a sign that birthmarks have formed within the body.

Ultrasound exams take just a few minutes to complete.

MRI Scans

MRI scans use magnetic fields and radio waves to create detailed two- and three-dimensional images of tissues inside the body. A doctor may recommend MRI to visualize the extent or nature of a certain type of birthmark, such as a deep hemangioma, if ultrasound does not provide enough information.

MRI is also used to provide images of the brain if a doctor suspects that abnormal cell growth related to a birthmark may be present in other parts of the body. This may occur, for instance, if you have a very large congenital nevus birthmark.


Our doctors may recommend a biopsy if your child has a mole present at birth that looks unusual. During a biopsy, the doctor removes a small piece of the skin at the site of the birthmark and sends it to a lab, where it is examined under a microscope. Doctors inject a local anesthetic in the skin surrounding the birthmark to eliminate pain during the procedure.

Biopsies usually take place in a doctor’s office and take 15 to 30 minutes to perform. The small incision may be closed with stitches, and a bandage is applied. The skin usually heals in 7 to 10 days. A return visit for removal of the stitches may be required.

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