Collision tumor, a metastatic melanoma within a meningioma: a case report.

BACKGROUND: Collision tumors, involving two distinct neoplasms in a single anatomical site, are rare. Among these, the metastasis of melanoma into an intracranial meningioma is particularly uncommon, with only four previously reported cases. Melanoma, known for its aggressive metastatic potential, contrasts sharply with the small number of collision tumor reports. The coexistence of these tumors poses diagnostic and therapeutic challenges, particularly in patients with a stable meningiomas.

RESULTS: We present the fifth documented case of melanoma metastasizing to a meningioma, the first to include genetic analysis revealing an NRAS mutation in the melanoma. The patient, a 58-year-old man, developed a hemorrhagic transformation of a stable left frontal meningioma. Surgical resection confirmed a biphasic tumor with melanoma cells infiltrating the meningioma. Despite initial treatment with immune checkpoint inhibitors, the patient's condition progressed with widespread metastatic melanoma, ultimately leading to death.

CONCLUSIONS: The rarity of reported melanoma-to-meningioma metastasis highlights the need for further research into the genetic and pathophysiological mechanisms underlying tumor-to-tumor metastasis. Advances in genomic technologies could help identify biomarkers associated with such rare phenomena. This case also emphasizes the importance of monitoring patients with stable meningiomas and a history of melanoma for potential metastasis. Future research should explore whether prophylactic management of benign meningiomas could mitigate this risk and assess the long-term outcomes of collision tumors compared to typical metastatic brain tumors.