Epidemiological aspects of skin melanoma in the Republic of Kazakhstan

Background: A 7-year-old female with no significant medical history presented with an enlarging lesion on the thigh.On physical examination, the patient had a 1x1cm, pedunculated, skin-colored, papillomatous papule.The lesion had been present since birth and had enlarged over the past few months.Methods: An excisional biopsy revealed a poorly circumscribed dermal proliferation composed of atypical melanocytes arranged in nests and sheets throughout the superficial and deep dermis.The melanocytes exhibited marked cytologic atypia, including large epithelioid and spindled cells with abundant eosinophilic cytoplasm and prominent nucleoli.Atypical mitotic figures were observed throughout the entire lesion.Immunohistochemical stains showed positivity for Panmel, SOX-10, and p21; HMB-45 was focally positive, and p16 was significantly diminished.Results: These findings were consistent with Spitz Melanoma with a Breslow depth of at least 5mm.Additionally, RNA sequencing identified a MAP3K:SVIL fusion transcript, which leads to MEK/ERK activation.Sentinel lymph node biopsy was positive for two lymph nodes, and further workup showed no distant metastatic disease.With an initial diagnosis of malignant melanoma, pT4a N2a M0, stage IIIC, immunotherapy was prescribed for one year.Currently, eight months after immunotherapy was suspended, the patient is under workup for suspected relapsed melanoma.Conclusions: Pediatric melanoma is extremely rare; less than 1% of all cases of melanoma occur before the age of 18. Clinically, many lesions do not meet the classic ABCDE criteria, and a higher frequency of atypical presentations with nodular and amelanotic lesions have been reported, hindering the diagnosis.From a histological perspective, there are three main subtypes of pediatric melanomas: Spitzoid melanomas, melanomas arising from congenital nevi, and conventional melanomas.Spitzoid melanoma is the most common subtype in pre-puberty patients, such as in our case.MAPK-activating mutations have been reported in both adult and pediatric Spitz melanomas.However, there is no sufficient genomic data to support the use of molecular testing for diagnosis, and the gold standard for diagnosis remains histopathological assessment.The key clinical and epidemiological features, histological findings, and prognostic features of pediatric melanoma remain poorly defined.We share this remarkable clinical case to raise awareness of this challenging diagnosis.