A small congenital nevus (Figure 144-1) was noted on this 6-month-old child by his new family physician during a routine exam. The parents acknowledged that it was present from birth and asked if it needed to be removed. They were reassured that nothing needs to be done about it and unless there were suspicious changes in the future it could remain there for the remainder of their child’s life.
Garment nevus, bathing trunk nevus (Figure 144-2), giant hairy nevus, giant pigmented nevus, pigmented hairy nevus, nevus pigmentosus, nevus pigmentosus et pilosus (pigmented nevus with hair).1
Tardive congenital nevus refers to a nevus with similar features to congenital nevi, but appears at age 1 to 3 years.
CMN develop in 1 to 6 percent of newborns and are present at birth or occasionally develop during the first year of life.1 In a recent case series in California (N = 594), 2.4 percent of the infants had CMN.2
In an Italian prevalence study of over 3000 children aged 12–17 years, congenital melanocytic nevi or congenital nevus-like nevi were found in 17.5 percent; most (92%) were small (<1.5 cm).3
Congenital nevi are also seen in neurocutaneous melanosis, a rare syndrome characterized by the presence of congenital melanocytic nevi and melanotic neoplasms of the central nervous system.
The development of melanoma within CMN (Figure 144-8) is believed to occur at a higher rate than in normal skin. Estimates range from 4 to 10 percent with smaller lesions having lowest risk.1
In a systematic review, 46 of 651 patients with CMN (0.7%) followed for 3.4 to 23.7 years developed melanomas, representing a 465-fold increased relative risk of developing melanoma during childhood and adolescence.4 The mean age at diagnosis of melanoma was 15.5 years (median 7 years).
Patients with giant CMN (larger than 20 cm; Figures 144-2 to 144-5) appear to be at highest risk where subsequent melanoma has been reported in 5 to 7 percent by age 60 years.5 In one study, 70 percent of patients who had a large CMN diagnosed with melanoma were diagnosed within the first 10 years of life.6
However, in a prospective study of 230 medium-sized congenital nevi (1.5 to 19.9 cm; (Figures 144-6 to 144-7) in 227 patients from 1955 to 1996, no melanomas occurred. The average follow-up period was 6.7 years to an average age of 25.5 years.7
Other risk factors for melanoma include personal or family history of melanoma or other skin cancer, presence of multiple nevi, red hair, blue eyes, freckling, and history of radiation (see Chapter 147, Melanoma).1
FIGURE 144-3
Bathing trunk congenital melanocytic nevus has fine velus hairs on the surface. In time, these hairs become terminal hairs and the lesion could then be termed congenital hairy nevus. It has a significant premalignant potential. Staged excisions are often performed to debulk the lesion even if it cannot all be removed. Careful clinical follow-up is required on at least an annual basis at the physician’s office and monthly at home looking for any changes that would prompt biopsy to exclude malignant degeneration. (Image used with permission from Robert Brodell, MD.)
FIGURE 144-6
Congenital nevus on around the areola of a 4-month-old girl. It was recommended to not excise this nevus as it would likely cause damage to breast development in the future. As there are no malignant features this nevus will be followed with yearly clinical exams. (Used with permission from Richard P. Usatine, MD.)
The etiology of CMN is unknown.
Congenital nevi result from a proliferation of benign melanocytes in the dermis, epidermis, or both. Melanocytes of the skin originate in the neuroectoderm and migrate vertically to the skin and other locations such as the central nervous system and eye.1 Defects in migration or maturation are hypothesized as causal.
