Giant congenital nevus

Alternative Names

Congenital giant pigmented nevus; Giant hairy nevus; Giant pigmented nevus; Bathing trunk nevus; Congenital melanocytic nevus – large

Definition of Giant congenital nevus

A congenital pigmented or melanocytic nevus is a dark colored, often hairy patch of skin that is present at birth.

Causes, incidence, and risk factors

Bathing trunk are thought to be caused by defects or problems that occur as a baby grows in the womb. However, in some families bathing trunk nevus may be inherited.


A nevus will appear as dark-colored patch with any of the following:

Signs and tests

All birthmarks should be evaluated by your health care provider. A biopsy of suspicious areas may be obtained for examination to determine if the cells have become cancerous. An MRI of the brain might be performed if the lesion is over the spine.


Treatment consists of frequent examination to check for skin cancers and, when possible, surgery to remove the nevus. Skin grafting is done when necessary. Larger nevi may need to be removed in several stages.

Expectations (prognosis)

Skin cancer (such as malignant melanoma and other types) may develop in up to 15% (1 out of 6) of people with larger or giant nevi, often in childhood. The risk is higher for larger or giant congenital nevi located on the back or abdomen.


Michael Lehrer, MD, Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 4/28/2009

Congenital nevus on the abdomen

ADAM Medical Encyclopedia

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