Primary intradural intramedullary melanocytoma of the spinal cord: illustrative cases.

backgroundPrimary intradural intramedullary melanocytomas of the spinal cord are exceedingly rare neoplasms. Their optimal treatment remains ill-defined because their imaging characteristics, molecular profile, and prognosis are poorly characterized. OBSERVATIONS: The authors first present the case of a 71-year-old male with low back pain, lower extremity weakness, sensory loss, and urinary incontinence who was found to have an enhancing conus mass requiring T11-L1 laminectomy and subtotal tumor resection. The tumor was positive for BAP1 inactivation and GNAQ mutations. The patient demonstrated partial neurological improvement, with residual motor deficits, and was subsequently counseled regarding radiation therapy. Then the authors present the case of a 65-year-old male with back pain, gait instability, and chronic progressive numbness of the torso and lower extremities who was found to have an intradural intramedullary mass for which T4-9 laminectomy and T5-8 laminoplasty with gross-total resection were performed. After recurrence, a revision T4-9 laminectomy was performed with incomplete tumor resection, and the patient underwent adjuvant radiotherapy. LESSONS: These cases demonstrate that molecular characterization, such as BAP1 inactivation or GNAQ mutation, offers valuable prognostic insights and may inform the need for adjuvant therapies including chemotherapy, radiotherapy, or close surveillance. https://thejns.org/doi/10.3171/CASE25946.