Intratumoral hemorrhage from brain metastases following nivolumab therapy for malignant melanoma: illustrative case.

Malignant melanoma is a highly aggressive type of cancer that frequently causes brain metastases, leading to poor outcomes. Immune checkpoint inhibitors (ICIs), such as nivolumab, play a crucial role in treating metastatic melanoma, yet intracranial hemorrhage (ICH) is a rare but serious complication. Although pseudoprogression and hyperprogressive disease are recognized phenomena associated with ICIs, the precise mechanisms connecting ICIs to ICH are not yet fully understood. The authors report the case of a 75-year-old man with stage IV malignant melanoma who experienced an ICH 5 days after starting nivolumab monotherapy. Imaging revealed a hemorrhagic brain metastasis in the left temporal lobe, necessitating a craniotomy. Histopathology confirmed melanoma metastasis without signs of pseudoprogression or hyperprogressive disease. The patient received whole-brain radiation therapy after surgery but continued to exhibit persistent aphasia and cognitive decline deficits. Early-phase intratumoral hemorrhage can occur shortly after ICI therapy, presenting diagnostic and management challenges. While this complication may result from the tumor's inherent hemorrhagic potential or ICI-induced changes such as pseudoprogression, hyperprogressive disease, or tumor lysis, its precise cause often remains unclear. Close monitoring during ICI treatment is essential to promptly address these potentially life-threatening events. https://thejns.org/doi/10.3171/CASE2581.