CNS metastatic renal cell carcinoma radiologically mimicking nerve sheath tumors: illustrative cases

BACKGROUND: Renal cell carcinoma (RCC) shows unpredictable, often delayed metastatic behavior, and CNS involvement carries significant morbidity. Rare metastases to cranial and spinal nerves can masquerade as benign nerve sheath tumors, causing misdiagnosis and treatment delays. Recognizing distinguishing features is essential to guide management. OBSERVATIONS: The authors present the cases of 3 patients with pathologically confirmed clear cell RCC metastatic to neural structures, presenting 6-9 years after nephrectomy. The sites included the cervical dorsal root ganglion, cerebellomedullary angle involving lower cranial nerves, and cerebellopontine angle mimicking trigeminal schwannoma. Initial MRI showed well-circumscribed, homogeneously enhancing masses with smooth margins and bony remodeling, favoring nerve sheath tumors. Closer review revealed atypical features including arterial spin labeling hyperperfusion, a susceptibility-weighted hemosiderin rim, vasogenic edema, and interval growth. PET/CT and biopsy confirmed metastatic disease. Management was individualized with radiosurgery, resection, and systemic therapy, achieving durable local control. LESSONS: Patients with prior RCC warrant a high index of suspicion for metastasis even when imaging suggests a benign nerve sheath tumor. Advanced MRI and PET/CT help identify features atypical for schwannoma and locate the safest biopsy site. When feasible, pathological diagnosis should precede definitive local therapy to inform radiosurgical dose, surgical planning, systemic therapy, and prognosis. https://thejns.org/doi/10.3171/CASE26518.