Abstract
Introduction: The synchronous occurrence of melanomas of varying histological types is an uncommon event, with reported incidences ranging from 0.2% to 8.6%. Case Report: We present the case of a patient diagnosed with Stage IIB nodular melanoma and Stage IIIC epithelioid cell melanoma within a 3-month period. After surgical excision of both lesions, lymph node enlargement was observed in the obturator region, indicating metastatic spread. As a result, combined immunotherapy with nivolumab and ipilimumab was initiated. Nivolumab and ipilimumab were administered at doses of 1 and 3 mg/kg, respectively, every 3 weeks for a total of four doses. Thereafter, treatment was continued with nivolumab alone at a dose of 3 mg/kg every 2 weeks. The patient underwent three cycles of immunotherapy, initially combined with intravenous methylprednisolone, later transitioned to an oral regimen with dexamethasone. The patient initially demonstrated a favorable clinical response without adverse effects. However, after the third infusion, severe diarrhea developed, leading to daily fluid losses exceeding 8 L and associated hypokalemia. Therefore, methylprednisolone was administered intravenously (2 mg/kg/day). Additionally, the patient experienced a splenic infarction that resolved spontaneously without resulting in asplenia. At the most recent follow-up evaluation, no lymph node enlargement was detected, and surveillance continues at 3-month intervals. Discussion: Although rare, the simultaneous emergence of melanomas at distinct anatomical sites underscores the necessity for increased patient vigilance and comprehensive clinical monitoring to facilitate early detection and timely intervention. Conclusion: Prompt initiation of targeted immunotherapy may improve patient prognosis and outcomes.