A Spitz nevus is a rare, benign melanocytic lesion, often referred to as a Spitz tumor. It is a non-cancerous skin growth composed of the same pigment-producing cells found in common moles. This lesion is also known as an epithelioid and spindle-cell nevus, reflecting the unique cell shapes seen under a microscope. Spitz nevi receive significant attention in dermatology because their appearance can be remarkably similar to that of malignant melanoma, the most serious form of skin cancer.
Characteristics and Presentation
The typical Spitz nevus often presents as a solitary, dome-shaped papule or nodule on the skin. While they can be pigmented, a classic Spitz nevus commonly appears pink, red, or reddish-brown due to the presence of blood vessels. The lesion usually grows rapidly for a few months before stabilizing, often reaching a size of less than one centimeter in diameter.
These growths occur most frequently in children and adolescents, though they can appear at any age. Common locations include the head, neck, and lower extremities, such as the legs. The rapid, isolated appearance of a firm, well-defined nodule often prompts a medical visit.
The fast initial growth of a Spitz nevus is one of its defining features, contrasting with the slow development of common moles. Some pigmented variants, often called Reed nevi, may appear darker and exhibit a unique starburst pattern under magnification.
Differentiating Spitz Nevus from Melanoma
The primary challenge in managing a Spitz nevus is the difficulty in distinguishing it from a spitzoid melanoma, as both can share similar features upon initial examination. The cells within a Spitz nevus—the epithelioid and spindle cells—are large and atypical-looking, mimicking the cellular structure of cancer. This histological resemblance necessitates a meticulous, multi-step diagnostic process.
The initial assessment often involves dermoscopy, a non-invasive procedure using a specialized magnifying lens to examine the skin surface and subsurface structures. Dermoscopy of a classic pigmented Spitz nevus frequently reveals a highly organized “starburst” pattern, characterized by symmetric, radial streaks extending from the center. In contrast, a spitzoid melanoma often displays asymmetry, atypical vascular patterns, a blue-whitish veil, and an irregular pigment network.
A definitive diagnosis, however, relies on complete surgical excision and subsequent histopathological examination by an experienced dermatopathologist. The pathologist examines the cellular architecture for specific benign indicators, such as symmetry and circumscription of the entire lesion. A critical feature is the phenomenon of maturation, where the melanocytic cells become smaller and more spindled as they descend deeper into the dermis.
The presence of eosinophilic globules known as Kamino bodies along the dermoepidermal junction also favors a benign Spitz nevus diagnosis. Conversely, features pointing toward malignancy include lack of maturation with depth, high mitotic activity deep within the lesion, and asymmetry. For the most ambiguous cases, advanced molecular testing, which identifies specific genetic fusions or mutations, is used to classify the tumor as benign, malignant, or an intermediate atypical Spitz tumor.
Treatment and Monitoring Protocols
Once a Spitz nevus is diagnosed, the management approach is determined by the certainty of the diagnosis and the patient’s age. For lesions that have been completely excised and confirmed by expert pathology as a classic, benign Spitz nevus, no further treatment is required. The excision is performed primarily to obtain the necessary tissue for the definitive microscopic diagnosis.
For lesions with any atypical features, or for those in which the pathology is equivocal, complete surgical re-excision with clear margins is the standard of care. In cases of classic Spitz nevi in children, where the diagnosis is highly confident, some dermatologists may recommend a watchful waiting approach. This non-surgical option involves regular, close monitoring of the lesion for any changes in size, shape, or color over time.