SAN FRANCISCO Histopathologic features of scalp nevi in children and adolescents that overlap with features of Clark's or dysplastic nevi also can be seen in scalp nevi in young adults, results of a study of 89 hairline and scalp nevi found.
The features may trigger melanoma concerns, so it is important to be aware of them to improve diagnostic accuracy and prevent unnecessary concerns or overtreatment, Dr. Betsy N. Perry said at the annual meeting of the American Society of Dermatopathology.
The nevi in this review came from 84 patients (ages 335 years) whose samples were filed in the dermatopathology service at the University of California, San Francisco. They showed characteristics common to other "nevi of special sites" such as melanocytic nevi on acral surfaces, genitalia, flexural areas, the breast, and in and around the ear, she and her associates reported.
In 63 (95%) nevi from 66 children and adolescents (aged 318 years) and in 19 (83%) of 23 nevi from young adults (aged 1935 years), the lesions contained large nests of cells that were composed primarily of pigmented epithelioid melanocytes and/or were distributed irregularly along the dermal-epidermal junction. More often than not, the melanocytes extended onto hair follicles and other adnexal structures in large nests or singly or in small clusters. Adnexal involvement was seen in 44 nevi (67%) from children/adolescents and 14 (61%) from young adults.
The findings support previous reports of these characteristics in scalp nevi of children and adolescents. "These are also seen in young adults, which is something that was not really clear in the literature before," said Dr. Perry of the University of Utah, Salt Lake City.
Suprabasilar scatter was rare, and seen in five (8%) nevi in children and adolescents and in none of the nevi from adults.
Among architectural features, squaring or bridging of the rete was common. Squaring was seen in 51 nevi (77%) in children/adolescents and 22 nevi (96%) in adults, and bridging was found in 61 nevi (92%) in children/adolescents and 20 (87%) in adults. "In some of the lesions, a concomitant congenital pattern was appreciated" in 25 (38%) of nevi in children/adolescents and in 5 (22%) in adults, she said.
Epithelioid melanocytes were very common, and appeared in 64 (97%) of nevi from children/adolescents and 22 (96%) from adults, Dr. Perry emphasized. Other cytologic features included atypical melanocytes in only three (5%) of nevi in children/adolescents and in none from adults.
"When cytologic atypia occurred, it was rare, and could either be in the epidermal or the dermal component," she said.
Dusty melanin commonly was present within keratinocytes, which is not known to have clinical significance but as a practical matter can make it difficult to determine circumscription and to look for melanocytes within these lesions, she added. In 33 (50%) of nevi from children/adolescents and 15 (65%) from adults, dusty melanin was present in keratinocytes.
Stromal features that were observed in most samples included lamellar fibrosis in 62 nevi (94%) from children/adolescents and in all nevi from adults. Lymphocytic infiltrate was seen in 55 nevi (83%) from children/adolescents and in 16 (70%) from adults. Melanophages appeared in 58 nevi (88%) from children/adolescents and in 18 (78%) from adults.
All nevi in the study had been removed from patients because they appeared clinically atypical.
These findings support results of two 2001 studies that characterized scalp nevi in children and adolescents and showed that they share features with "nevi of special sites."
A more recent analysis of atypical nevi of the scalp found features that were not commonly ascribed to either Clark's or "dysplastic" nevi in 4 (10%) of 39 nevi from adolescents but not in 30 nevi from children or 160 nevi from adults (J. Cutan. Pathol. 2007;34:3659).