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.

Smaller in infants and children, they usually continue to grow along 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 nevus may be inherited.

Bathing trunk nevus may occur with:

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

Smaller congenital pigmented or melanocytic nevi can be common in children and are less dangerous. However, larger or giant nevi are fairly rare.