Spitz Nevus in a Nevus Spilus: Management Considerations in Pediatric Patients

AFFILIATIONS:
¹Department of Graduate Medical Education, Tripler Army Medical Center, HI
²Department of Dermatology, Naval Medical Center, Portsmouth, VA

CITATION:
Flint RL, Cantor AS. Spitz nevus in a nevus spilus: management considerations in pediatric patients. Consultant. 2023;63(5):e7. doi:10.25270/con.2023.03.000005

Received September 23, 2022. Accepted January 12, 2023. Published online March 21, 2023.

DISCLOSURES:
The authors report no relevant financial relationships.

ACKNOWLEDGEMENTS:
None.

DISCLAIMER:
The authors report that informed patient consent was obtained for publication of the images used herein.
CORRESPONDENCE:

Rachel L. Flint, MD, Department of Graduate Medical Education, Tripler Army Medical Center, 1 Jarrett White Road, Honolulu, HI 96859 (rachflint@gmail.com)

Case presentation. A 4-year-old girl presented to the dermatology clinic with a 9 mm firm, nontender, well-circumscribed dome-shaped pruritic pink papule on her anterior left thigh. The papule was eccentrically located within a 4 cm tan ovoid patch with several darker brown macules, consistent with a nevus spilus (Figure 1).

Figure 1. A 9 mm firm, nontender, well-circumscribed, dome-shaped pruritic pink papule eccentrically located within a 4 cm tan, ovoid patch with several darker brown macules on the anterior left thigh.

Patient history. Her medical and family history was not significant for skin cancer. While the nevus spilus had been present since infancy and was previously tracked as a café-au-lait macule, the new pink papule developed within the past year, prompting her referral to a dermatologist.

Diagnostic testing. Dermatoscopy of the papule showed an asymmetric distribution of dotted spiral vessels surrounded by orthogonal shiny white lines (Figure 2). No inguinal lymphadenopathy was present. The differential diagnosis included Spitz nevus, melanoma, hemangioma, mastocytoma, and lymphocytoma.

Figure 2. Dermatoscopy of the 9 mm pink papule on the anterior left thigh revealing a distribution of dotted spiral vessels surrounded by orthogonal shiny white lines.

Treatment and outcome. Considering the asymmetric features of the lesion along with parental concern, excision with narrow margins was performed under sedation. Histology and immunohistochemical markers were consistent with a benign Spitz nevus. The excision site healed well with no recurrence or development of new lesions within the nevus spilus that remained.

Discussion. Nevus spilus is a cutaneous lesion characterized by multiple pigmented macules or papules within a pigmented patch. Lesions range from small and isolated (<20 cm) to giant (>20 cm) or zosteriform and may be associated with heritable syndromes.¹ These lesions exhibit activating HRAS mutations and are thought to create a favorable environment for subsequent nevi of any type.^2-4 Spitz nevi most commonly arise in prepubertal children and are classically pink or brown papules or nodules with distinct dermatoscopic features composed of epithelioid or spindle cell melanocytes. They can arise spontaneously or in association with an underlying lesion⁵ and share activating HRAS mutations when developing within a nevus spilus.² Nevus spilus and Spitz nevus are both uncommon in the general population. Both types of lesions have very low rates of malignant transformation and co-occurrence does not seemingly affect this rate.

Nevus spilus is most commonly found on the torso and extremities.⁶ They have increased expression of epidermal and vascular endothelial growth factors, which theoretically create a local environment favorable for the growth of new lesions.⁵ Neoplasms that develop within a nevus spilus can be benign or malignant. Rates of developing benign neoplasms are not quantified in the literature, most likely due to their benign nature. The reported risk for malignant neoplasm development is very low, estimated at 0.13% to 0.2%.⁷ Characteristics of nevus spilus associated with increased risk for malignant transformation include presence since birth, diameter greater than 4 cm, and giant or zosteriform morphology.⁸

Fewer than 25 cases describe Spitz nevi arising within a nevus spilus.^2,3,5,9,10 The most common dermatoscopic patterns of Spitz nevi are starburst, thick reticular network, globular, homogeneous pink, homogeneous black lamella, negative pigment network, and atypical/multicomponent.¹¹ In pediatric patients, Spitz neoplasms typically have a benign course.^12-16 Recent reports suggest the incidence of Spitzoid melanoma in pediatric populations is low, between 0.38% and 0.5%.^12,13 The incidence of childhood melanoma is also very low, and the most common histopathologic subtypes are superficial spreading melanoma and nodular melanoma.^17,18 Superficial spreading melanoma has a broad range of appearances, including irregular borders and pigmentation or a discrete focal area of darkening within a preexisting nevus. Nodular melanoma can be dark blue-black, bluish-red, or amelanotic with the presence of atypical vascular structures on dermatoscopy.^17,19 It can be difficult to distinguish homogenous pink and atypical/multicomponent Spitz nevi from melanoma on clinical examination, in which case referral for expert evaluation is recommended.

No standard guidelines exist for the management of these neoplasms. Recommended management of Spitz neoplasms varied in the past, but current literature favors a conservative approach given the rarity of melanoma in prepubescent children, rarity of fatal melanoma in prepubescent children, and rarity of fatal outcomes from all Spitz lesion subtypes in pediatric patients.^12-16 In the absence of concerning features, such as bleeding, evolution, or friability, excision is not routine for clinically-stable, typical-appearing, and dermatoscopically banal Spitz tumors.^12,13 For conservative management, the frequency of recommended clinical monitoring varies. Lallas and colleagues²⁰ suggest that typical-appearing, flat, pigmented Spitz nevi in children do not need to be monitored further. If conservative management is chosen, then patient and parent education is important so that any new or atypical features are evaluated promptly.¹² Biopsy considerations should be referred to a dermatologist, as histologic diagnosis depends on complete excision and visualization of the neoplasm base.

There are several external factors to consider when choosing treatment for patients with these neoplasms. Our facility had the resources and capabilities for pediatric sedation during excision. Additionally, in practices where patients may be seen by more than one physician, consistent follow-up with the same physician for conservative monitoring may not be guaranteed. We decided to excise our patient’s neoplasm, given the initial diagnostic uncertainty and parental concern. Excision of the remaining nevus spilus is not recommended.

We know that nevus spilus contains activating HRAS mutations and shares these HRAS mutations with the Spitz nevi developing within them, presumably from an additional second hit mutation.^2,3,6 Further investigation into the cause of the second hit mutation and its implication for why neoplasms developing in a nevus spilus are not reported is warranted. Notably, most Spitz nevus studies focus on a solitary lesion, not a Spitz nevus that developed within another lesion, as with our case. Though Spitz neoplasms in the pediatric patient are typically benign, the recurrence rate of these neoplasms in the “fertile field” of a nevus spilus is also unknown. Optimal management remains the center of debate, balancing conservative monitoring with excision. In cases of diagnostic uncertainty, expert evaluation by a dermatologist is important for risk stratification and optimal management.