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.

A giant congenital nevus is smaller in infants and children, but it usually continues to grow with the child. A giant pigmented nevus is larger than 8 inches once it stops growing.

Causes, incidence, and risk factors:

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

A bathing trunk nevus may occur with:

• Growth of fatty tissue cells (lipomas)
• Neurofibromatosis
• Other nevi
• Spina bifida

Smaller congenital pigmented or melanocytic nevi are common in children and lead to fewer complications. Larger or giant nevi are fairly rare.