What are Congenital Nevi?
Congenital nevi fall under the umbrella of pigmented lesions. These may be in the form of congenital melanocytic nevi (CMN), spitz nevus, or sebaceous nevus.
Congenital melanocytic nevi are present at birth, and are formed by a collection of pigmented melanocytes found in the skin (dermis and epidermis). They are found in 1 to 6% of newborn infants. They may range in presentation as a solitary plaque that changes in size in proportion to the child’s growth, or multiple lesions with at least one larger in size surrounded by satellite nevi. This latter type may also involve bone and the central nervous system (CNS), termed neurocutaneous melanosis, a rare syndrome that includes melanocytic tumors of the CNS. Congenital melanocytic nevi are divided into three groups based on their size: small (<1.5 cm in diameter), medium (1.5 – 19.9 cm), and large/giant (>20 cm). They can be found on any location in the body.
|Testing and Diagnosis|
In most cases of CMN, biopsies are not needed. However, surgical excision may be warranted in lesions that demonstrate significant change in appearance, growth, color variation, or ulceration. Though the majority of these lesions are benign, the underlying cells have the potential to transform into melanoma. Generally speaking, the risk of malignant change in small and medium CMN is less than 1%, while for giant CMN, approximately 5%. Treatment depends on size, location, age, potential for malignant transformation, and cosmetic result. Small and medium sized nevi can be monitored and removed if the patient would benefit cosmetically, or if the lesion begins to change. Excision may be straightforward with primary closure in the case of smaller lesions, or may require reconstructive strategies such as tissue expansion, skin grafts, or local tissue flaps and rearrangements to close the defect. Lasers are not often recommended as recurrence may occur and malignant transformation of deeper tissue may persist and become difficult to detect. Removal of giant lesions may require several stages in addition to the previous reconstruction techniques.
A spitz nevus is a benign melanocytic nevus that most frequently occurs in children but can also arise in adults. They are usually in the head and neck region with some involving the trunk or extremities. They appear as well-circumscribed raised pink lesions that can rapidly increase in size. Histologically (under the microscope), spitz nevi resemble melanoma and were previously termed juvenile melanoma. However, they do not behave in malignant fashion and are thus distinctly benign. When suspected they should be removed completely.
Nevus sebaceous is found in 0.3% of newborns and usually presents as a solitary lesion at birth or early childhood. They appear as a velvety plaque mostly on the scalp or head and neck region as a hairless patch. The surface may be scaly, and appear skin-toned or pink, yellow, orange or tan. They are composed of sebaceous glands (which secrete an oily matter that lubricates the skin). There is a risk for malignant transformation, though this is low. However, given its location often in the hair-bearing scalp monitoring of the lesion may be difficult. Thus, surgical excision may be warranted.