Lesions That May Become Melanoma
Sometimes distinguishing a melanoma from a regular mole is easy, because the melanoma looks so dramatically different from all the other moles on one’s body.
However, sometimes the differences can be quite subtle. When a dermatologist cannot tell whether a mole is dangerous or not just by examination, it becomes necessary to cut out all or a piece of the mole for further examination by a pathologist.
A pathologist is a physician who specializes in examining tissue samples microscopically to determine the difference between benign and malignant cells.
A dermatopathologist is a specialized pathologist who only looks at skin biopsies and is very good at determining if there is any cancer present.
Two types of pigmented lesions are associated with an increased risk of developing melanoma:
- Congenital nevi
- Atypical nevi
These are moles that you are born with or that appear in early infancy. They are uncommon, appearing in only about 1% to 2% of all newborns.1,2,3
A 4-month old infant with giant congenital nevi, along with other additional lesions
- The risk of developing a melanoma is directly related to the size of the congenital nevus.
- Studies that have investigated the risk of a small or medium congenital nevus turning into a melanoma have put the lifetime risk at between 0% – 5%.
- The risk for giant nevi (also known as garment nevi), which cover major areas of the head or body, is less clear. Historically, some studies reported a very high lifetime risk (up to 50%). Recently, larger studies have placed the lifetime risk at closer to 10% – 12%.4
Atypical Nevi (dysplastic nevi)
These are not ordinary moles. They appear generally larger, with irregular or indistinct borders and variations of color within the mole, ranging in color from pink to dark brown.
Sometimes they are described as looking like fried eggs, with a raised center of darker pigmentation surrounded by a flat, lighter area. Atypical nevi may occur anywhere on the body, but are found most frequently on the back and on sun-exposed areas.
A dysplastic nevus, with irregular margins and variegated color
- The vast majority of atypical nevi do not become melanomas. However, having atypical nevi is a risk factor for melanoma.
- FAMM syndrome (Familial Atypical Mole and Melanoma), also called dysplastic nevus syndrome, is an inherited condition where affected individuals develop many moles (usually at least 50 to 100) and their moles are often atypical.
1. Walton RG, Jacobs AH, Cox AJ. Pigmented Lesions in Newborn Infants. Br J Dermatol.1976;95:389-396.
2. Goss BD, Forman D, Ansell PE, et al. The Prevalence and Characteristics of Congenital Pigmented Lesions in Newborn Babies in Oxford. Pediatr Perinat Epidemiol. 1990;4:448-457.
3. Rivers JK, Frederiksen PC, Dibdin C. A Prevalence Survey of Dermatoses in the Australian Neonate. J Am Acad Dermatol. 1990;23:77-81.
4. DeDavid M, Orlow SJ, Provost N, et al. A Study of Large Congenital Melanocytic Nevi and Associated Malignant Melanomas: Review of Cases in the New York University Registry and the World Literature. J Am Acad Dermatol. 1997;36(3 Pt 1):409-416.