Nevus Spilus, also known as Speckled Lentiginous Nevus, is a common type of pigmented lesion. It is characterized by a unique “nevus on nevus” appearance, which often prompts concern. This article clarifies the nature of Nevus Spilus and addresses its potential risk, classifying it as a generally benign skin mark that requires informed monitoring.
Defining Nevus Spilus
Nevus Spilus is a benign melanocytic lesion defined by two components: a light tan or light brown background patch and multiple smaller, darker spots scattered within it. The lighter area resembles a café-au-lait macule, characterized by uniform, faint pigmentation. Overlaid on this base are numerous small, dark brown or black macules and papules, often measuring between one and three millimeters in diameter, creating the distinctive speckled pattern.
The lesion is a nevoid disorder involving an overgrowth of pigment-producing cells called melanocytes. Nevus Spilus can be congenital or develop early in childhood, often before age two. The lighter patch is usually visible first, with the darker speckles developing later, sometimes around puberty or into adulthood. While it can appear anywhere, it is most commonly found on the trunk and extremities.
Understanding the Risk Profile
Nevus Spilus is classified as a benign skin finding, meaning it poses no danger for most people. However, because the darker spots are collections of nevus cells, there is a statistically low, documented risk of malignant transformation into melanoma. This transformation is rare, with an estimated risk ranging from approximately 0.13% to 0.2% over a lifetime. This probability is significantly lower than the risk associated with certain other types of congenital birthmarks.
The potential for malignancy is primarily linked to the darker, more concentrated melanocytic areas (the speckles), not the lighter background patch. The most common type of skin cancer arising within Nevus Spilus is superficial spreading melanoma. A slightly heightened risk may be associated with lesions larger than four centimeters, those that are congenital, or those that follow a segmental or zosteriform distribution. Despite these factors, the risk remains very low, based on the small number of associated melanoma cases reported.
Diagnosis and Differentiation
The diagnosis of Nevus Spilus is typically made by a dermatologist through a thorough clinical examination and visual assessment. The speckled pattern on a uniform light base is usually sufficient to distinguish it from other pigmented lesions. It must be differentiated from simple café-au-lait macules, which lack the darker spots, or agminated nevi, which feature clustered moles without the light background patch. A correct diagnosis is important to rule out more concerning conditions like early melanoma or large congenital nevi.
Dermoscopy, a non-invasive technique using a specialized magnifying tool, is frequently used to confirm the diagnosis and monitor the lesion over time. This tool allows the physician to visualize deeper structural details and pigment patterns. A biopsy may be indicated if the lesion exhibits suspicious changes, such as rapid growth, irregular borders, or a shift in color, which are warning signs of potential malignancy. Histological analysis of a biopsy confirms the presence of benign nevus cells or identifies the rare occurrence of melanoma.
Monitoring and Management
The management of Nevus Spilus centers on diligent monitoring rather than routine preventative removal, given its benign nature. Individuals with this lesion should engage in regular self-examination, paying close attention to any changes in the darker speckles within the patch. The well-known ABCDE criteria—Asymmetry, Border irregularity, Color variation, Diameter greater than 6mm, and Evolving (changing) characteristics—serve as a helpful guide for detecting early signs of melanoma.
Routine check-ups with a dermatologist are recommended, often annually, to evaluate the lesion. During these appointments, the physician may use dermoscopy to document the lesion’s appearance and track subtle changes, sometimes using sequential digital imaging for comparison. Surgical removal is typically reserved for instances where malignancy is suspected based on clinical or dermoscopic findings, or for cosmetic reasons. Prophylactic excision of the entire Nevus Spilus is not generally recommended due to its low risk and the potential for scarring.