Agminated Spitz Naevi Arising Within a Congenital Naevus Spilus: A Diagnostic Challenge

Spitz naevi are benign melanocytic proliferations typically arising in childhood [1]. They usually present as solitary lesions but may, rarely, occur in agminated, dermatomal, or disseminated forms. The occurrence of agminated Spitz naevi within a congenital naevus spilus (speckled lentiginous naevus) is exceptionally uncommon, with few cases reported [2]. We describe the case of a 4-year-old girl with three nodules developing within a hyperpigmented patch on the dorsum of her right hand (Figure 1). The naevus spilus had been present since birth, with gradual darkening and speckling. Over the preceding 12 months, rapidly enlarging pink-red papules (3–4 mm) appeared within the lesion. There was no history of trauma, chemotherapy, or radiation exposure, and the patient was otherwise well, with no relevant family history. Examination revealed a speckled naevus spilus containing three well-circumscribed, non-tender papules. Dermoscopy showed symmetrically distributed dotted vessels within a homogenous pink background. A punch biopsy demonstrated dermal nests of epithelioid and spindle melanocytes with minimal melanin pigmentation and small eccentric nucleoli, consistent with Spitz naevus (Figure 2). No dysplastic or malignant features were identified. Given the benign histopathological findings, molecular studies and surgical excision were not pursued; however, a 6-month clinical follow-up was arranged for surveillance, with earlier review advised should parental concern arise. The occurrence of multiple Spitz naevi in a single patient is uncommon. In a review of the Yale Spitzoid Neoplasm Repository (1990–2010) comprising approximately 3000 specimens, only nine patients were identified with multiple Spitz naevi [2]. An agminated distribution within a naevus spilus is even rarer, with few cases reported in the literature [2]. Proposed triggers include trauma, chemotherapy, and immunosuppression [2]. Molecular studies have identified chromosome 11p amplification, harbouring the HRAS gene, in approximately 20% of Spitz naevi [3]. Although uncommon in melanoma, HRAS alterations have been reported in some spitzoid melanomas, limiting its specificity as a benign marker [3]. Clinically and dermoscopically, Spitz naevi are among the most challenging mimickers of melanoma. Spitzoid neoplasms are classified as typical Spitz naevus, atypical Spitz naevus, or spitzoid melanoma [3]. While dermoscopy is a valuable tool for typical cases, atypical or homogenous pink/red variants may display overlapping features with melanoma [4]. Although melanoma is exceedingly rare in prepubescent children, many clinicians seek histopathologic confirmation, given the potential consequences of a missed diagnosis [4]. Histologically, Spitz naevi exhibit dermal nests of epithelioid and/or spindle melanocytes with minimal atypia and low mitotic activity [3]. Ancillary immunohistochemical markers (S-100, Melan-A/Mart-1, HMB-45, Ki-67, cyclin D1, p15, p16) and molecular assays can assist in distinguishing benign from malignant spitzoid lesions, though their prognostic relevance remains unclear [3]. The International Dermoscopy Society recommends close observation of low-risk Spitz lesions in children (< 12 years of age, symmetrical, non-nodular, starburst pattern), with excision reserved for lesions exhibiting concerning changes [5]. Regular follow-up remains essential to monitor for evolution, recurrences, or new lesions. This case highlights the rare coexistence of agminated Spitz naevi within a congenital naevus spilus and emphasises the importance of clinicopathological correlation when assessing atypical spitzoid lesions. Emerging immunohistochemical and molecular tools may further refine diagnostic accuracy in challenging or borderline cases. The authors have nothing to report. Informed consent for publication of the case details and clinical images was obtained from the patient's guardian. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.