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

Background: 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.

Observations: 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.

Lessons: 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.