A Spitz nevus is a type of mole that often raises concern due to its resemblance to melanoma, a serious skin cancer. While generally benign, their visual similarities make accurate diagnosis challenging. This article clarifies the relationship between Spitz nevi and melanoma, exploring their distinct characteristics, diagnostic complexities, and potential for transformation.
What is a Spitz Nevus?
A Spitz nevus is a non-cancerous skin growth, a type of melanocytic nevus, meaning it is composed of melanocytes, the cells that produce skin pigment. These moles are relatively uncommon and are frequently observed in children and young adults, with about 70% of cases developing before the age of 20. However, they can appear at any age.
Clinically, a classic Spitz nevus typically presents as a dome-shaped papule that can be red, reddish-brown, or pink. Pigmented variants can appear tan, brown, or even bluish-black. They usually range from a few millimeters to one or two centimeters in diameter and are commonly found on the face or limbs. A notable characteristic is their initial rapid growth over a few months, after which they tend to become static or may even disappear spontaneously over time.
How Spitz Nevus Differs from Melanoma
The primary challenge with Spitz nevi lies in their ability to clinically and microscopically mimic melanoma, a malignant skin cancer. Dermatologists use specific features to differentiate them.
On clinical examination, while a Spitz nevus might be dome-shaped and uniformly colored, melanoma often exhibits asymmetry, irregular borders, varied colors, and a diameter larger than 6 mm. Dermoscopy, a technique using a magnifying tool to examine skin lesions, helps identify subtle patterns. Spitz nevi often show a “starburst” pattern or uniform arrangements of dotted vessels, while melanoma might display atypical networks, polymorphic vessels, or blue-whitish veils.
Under a microscope, pathologists look for distinct histological differences. Spitz nevi typically exhibit a symmetrical appearance with uniform nuclear enlargement and the presence of Kamino bodies, which are specific eosinophilic globules. Melanoma, in contrast, often shows asymmetry, lack of cellular maturation with depth, and a higher rate of cellular division (mitotic activity). Despite these distinguishing features, some Spitz nevi can display atypical characteristics that overlap with melanoma, making definitive diagnosis complex.
Spitz Nevus and the Risk of Melanoma
While a true malignant transformation of a benign Spitz nevus is exceedingly rare, the main concern arises from the diagnostic difficulty in distinguishing Spitz nevi from a specific type of melanoma known as spitzoid melanoma. Spitzoid melanoma is a malignant melanoma that shares significant clinical and histological similarities with Spitz nevi.
This diagnostic dilemma is particularly pronounced with “atypical Spitz nevi,” also referred to as atypical Spitz tumors (ASTs) or Spitz tumors of uncertain malignant potential (STUMP). These lesions possess features that fall between clearly benign Spitz nevi and overt melanoma, presenting a significant challenge for pathologists. Molecular tests may be used to identify genetic alterations characteristic of melanoma, such as specific gene mutations or translocations, which are typically absent in benign Spitz nevi.
In rare instances, a Spitz nevus might regress, and a melanoma could subsequently appear in the same location, or a Spitz nevus might genuinely evolve. However, these are exceptions, and the primary concern remains accurate initial differentiation. The probability of a spitzoid-looking lesion being melanoma increases with age, especially after puberty.
What to Do About a Spitz Nevus
Given the diagnostic complexities, managing a Spitz nevus often involves careful consideration and individualized approaches. For children under 12 years old, monitoring the nevus with digital dermoscopic surveillance, which involves taking photographs to track changes, is a common approach. This allows healthcare providers to observe the lesion’s growth and stability over time.
However, if a Spitz nevus exhibits atypical features, rapid changes, or if there is diagnostic uncertainty, surgical removal (excision) is typically recommended. This is especially true for older children and adults, where the distinction from melanoma becomes even more critical. A biopsy, which involves removing a tissue sample for laboratory analysis, is performed to obtain a definitive diagnosis.
Regular self-skin exams are important for anyone, particularly those with moles, to identify any new or changing lesions. Any mole that changes in size, shape, or color, or that bleeds or itches, should be promptly evaluated by a dermatologist. This proactive approach ensures that any suspicious growth is diagnosed and managed appropriately.