Malignant cutaneous adnexal neoplasms with distant brain metastasis: an aggressive behavior. Illustrative cases.

backgroundPrimary malignant cutaneous adnexal neoplasms are rare and can spread locally or to lymph nodes, and very infrequently to distant sites, such as the brain. Their management is poorly documented, and there are no established clinical practice guidelines for treatment. OBSERVATIONS: A 57-year-old male underwent surgery 2 years earlier for adenocarcinoma of the cutaneous adnexa of the right arm. He was admitted to the emergency department with a 15-day history of drowsiness, dysarthria, and signs consistent with frontal lobe involvement. Preoperative MRI revealed a heterogeneous left frontal lobe tumor with contrast enhancement of a solid mass. A craniotomy and complete tumor resection were performed. He then received radiosurgery (27 Gy). MRI studies at 1 and 6 months postoperatively showed complete resection. These tumors are rare and originate from hair follicles, sebaceous glands, or sweat glands. They have an overall 5-year survival rate of 78.2%, but the metastasis rate can range from 15% to 30%. The treatment approaches are not well described in the literature; combinations of surgery, chemotherapy, immunotherapy, targeted therapy, and radiotherapy are utilized. LESSONS: Malignant cutaneous adnexal neoplasms are rare conditions that need precise diagnosis and prompt multidisciplinary treatment. https://thejns.org/doi/10.3171/CASE25447.