INTRODUCTION AND IMPORTANCE: Melanoma is the fifth most common cancer diagnosed in the US in 2022. While its incidence increased from 1980 to 2017, it rarely happens in children. Its diagnosis and treatment are challenging in pediatric patients due to its rarity and different presentations compared to adults. CASE PRESENTATION: An 11.5-year-old boy with a complaint of back pain was admitted to the hospital. Initial examinations were normal
however, due to continued pain and symptoms (e.g., inability to walk, knee pain and ankle ecchymosis, weight loss, vomiting, nausea, and dyspnea), further examinations were performed. Biopsy, nuclear scan, computed tomography (CT) scan, and immunohistochemistry (IHC) confirmed the malignant melanoma diagnosis with bone and lung metastasis. Single-agent treatment with nivolumab was initiated after the diagnosis confirmation with no specific complication. The patient's parents decided to continue the treatment in their city of residence to reduce costs. However, the treatment was not continued, and unfortunately, the patient has passed away. CLINICAL DISCUSSION: Melanoma is rare in children, making its diagnosis challenging. There are no specific guidelines for treating melanoma in pediatric patients, especially in children under 12, with ongoing debate on the most suitable treatment and follow-up options for these patients. It is important to fully examine resected legions for malignancy. CONCLUSION: The study highlights the difficulties in diagnosing and treating malignant melanoma in children, considering its rarity and unusual signs and symptoms compared to adults. Specific guidelines are needed for diagnosing and treating malignant melanoma in pediatric patients.