A Spitz nevus is a benign skin growth made up of melanocytes, the cells that produce pigment. It most commonly appears in children and teenagers, with an average age of diagnosis around 15 years old. Though harmless in its classic form, a Spitz nevus gets attention because it can look strikingly similar to melanoma under the microscope, making accurate diagnosis essential.
What It Looks Like on the Skin
A classic Spitz nevus typically appears as a small, dome-shaped bump that is pink to red in color. The pink or reddish tone comes from increased blood vessel activity rather than pigment, which sets it apart from ordinary moles. About 10% of Spitz nevi are pigmented, ranging from tan and brown to even black. They tend to be symmetrical with smooth surfaces and clearly defined borders, and they’re usually less than a centimeter across.
One feature that can alarm parents and patients is how quickly a Spitz nevus can appear. A spot may go from normal-looking skin to a noticeable bump in a matter of weeks. This rapid growth is one of the reasons it often triggers a biopsy, since fast-growing skin lesions naturally raise concern. The most common locations are the arms (about 23% of cases) and the face (about 17%), though they can show up anywhere on the body. There is a slight female predominance, with girls and women accounting for roughly 55% of cases.
Why It Gets Confused With Melanoma
Under a microscope, Spitz nevi are made up of large spindle-shaped and epithelioid melanocytes arranged in nests. These cells can look atypical, and over half of Spitz nevi contain melanocytes that a pathologist would flag as unusual. This overlap with melanoma has caused diagnostic headaches for decades.
Several microscopic features help pathologists lean toward a Spitz nevus rather than melanoma. A Spitz nevus tends to be symmetrical, with evenly sized cell nests from one side of the lesion to the other. It often contains structures called Kamino bodies, which are small protein clumps found in about 25% of cases. The cells also “mature” as they go deeper into the skin, meaning they get smaller and more orderly toward the base of the lesion. In melanoma, the opposite tends to happen: cell division increases deeper in the skin, the growth is asymmetrical, and abnormal cell divisions are more common throughout.
Six features are most useful for telling the two apart. Symmetry, uniform cell nests, and Kamino bodies point toward a Spitz nevus. A high rate of cell division deep in the lesion, abnormal cell divisions, and dividing cells near the base of the growth point toward melanoma.
How Dermatologists Evaluate a Spitz Nevus
When a dermatologist examines a suspected Spitz nevus with a dermatoscope (a handheld magnifying device with polarized light), pigmented versions often show a distinctive “starburst” pattern: a dark blue-black center surrounded by symmetrical streaks radiating outward like rays. Other patterns include a globular pattern with evenly spaced round structures, or a homogeneous pattern with uniform coloring throughout. Over time, some Spitz nevi transition to a fading “stardust” pattern, which may signal the lesion is naturally involuting, or shrinking on its own.
If the clinical picture isn’t clear cut, a biopsy is the next step. The tissue sample is examined under a microscope, and in difficult cases, specialized staining techniques can help. Markers that measure how actively cells are dividing tend to be significantly lower in Spitz nevi than in melanoma, which provides another layer of diagnostic confidence.
The Spectrum: Classic, Atypical, and Spitzoid Melanoma
Dermatologists and pathologists now think of Spitz-type growths along a spectrum with three categories. At one end is the classic Spitz nevus, which is completely benign. In the middle sits the atypical Spitz tumor, which has some worrisome features under the microscope but doesn’t meet the criteria for melanoma. At the far end is spitzoid melanoma, a true cancer.
Atypical Spitz tumors occupy an uncomfortable gray zone. Long-term outcome studies show they carry minimal lethal potential but a moderate risk of spreading to nearby lymph nodes. In one study, sentinel lymph node biopsy was positive in about 1 out of 6 patients with atypical Spitz tumors, compared to 4 out of 8 with spitzoid melanoma. People diagnosed with an atypical Spitz tumor also face a somewhat higher long-term risk of developing melanoma, so ongoing monitoring matters.
Genetic Differences From Melanoma
At the DNA level, Spitz nevi carry a different set of genetic changes than melanoma. About 12% of Spitz nevi have extra copies of a section of chromosome 11 that contains a gene called HRAS. When those extra copies are present, roughly two-thirds of the time the HRAS gene also carries an activating mutation. Melanoma, by contrast, is more commonly driven by mutations in different genes (BRAF and NRAS are the most frequent). This molecular distinction is increasingly used in difficult diagnostic cases to help pathologists determine whether a lesion is truly a Spitz nevus or something more concerning.
How Spitz Nevi Are Managed
Management depends heavily on the patient’s age and the specific features of the lesion. Current guidelines take a tiered approach. In children under 12, a Spitz nevus with a classic, symmetrical starburst pattern on dermoscopy can generally be monitored rather than removed. The rationale is strong: no case of melanoma or atypical Spitz tumor displaying a symmetric starburst pattern has ever been documented in a prepubertal child. Monitoring involves periodic dermoscopic imaging to confirm the lesion is growing symmetrically or fading over time. Any asymmetric changes prompt excision.
For patients over 12, and for any lesion that is asymmetric or nodular regardless of age, excision is generally recommended. In adults, dermatologists are more cautious because the risk of a Spitz-like lesion actually being melanoma increases with age. Surveys of dermatologists in the United States found that 70% of general dermatologists and 80% of pediatric dermatologists recommend excision with 1 to 2 millimeters of normal skin around the lesion. A small percentage of general dermatologists recommend wider margins of 4 millimeters or more, though pediatric dermatologists uniformly keep margins under 4 millimeters.
If a biopsy shows atypical features and the margins aren’t clear (meaning some of the lesion may remain), re-excision is common. In one study, the majority of atypical Spitz nevi with positive margins after biopsy were re-excised with narrow margins averaging about 2 millimeters. This is a straightforward office procedure, and for classic Spitz nevi, complete removal is typically curative with no further treatment needed.
What to Expect After Removal
For a classic Spitz nevus, the prognosis after complete excision is excellent. These are benign growths, and once fully removed, they rarely recur. The excision site heals like any minor skin procedure, usually leaving a small scar. If the pathology report confirms a classic Spitz nevus with clear margins, no additional follow-up beyond routine skin checks is necessary.
For atypical Spitz tumors, closer follow-up is standard. Your dermatologist will likely schedule regular skin exams and may recommend imaging of nearby lymph nodes depending on the specifics of the pathology report. The overall outlook remains favorable, but the slightly elevated risk of lymph node involvement and future melanoma means that ongoing surveillance is a reasonable precaution.