A 65-year-old woman with a history of breast cancer and a recent melanoma presents to the emergency room following a tonic-clonic seizure. Blood chemistry values are within normal limits. There is no history of drug or alcohol use. MRI of the brain shows bilateral cerebral edema and a cystic, frontal lobe lesion. Frozen section obtained from a CT-guided biopsy reveals a hemorrhagic nodule of neoplastic cells. Immunohistochemical stains for which of the following antigens would be most helpful in making your diagnosis definitive for melanoma?

Metastatic tumors are the most common intracranial neoplasms. They reach the intracranial compartment through the bloodstream, generally in patients with advanced cancer. Tumors of different organs vary in their incidence of intracranial metastases. For example, a patient with disseminated melanoma has a greater than 50% likelihood of acquiring intracranial metastases, whereas the incidence of such metastases in carcinoma of the breast and lung is 35%, and the incidence for cancer of the kidney or colon is only 5%. HMB-45 is a useful tumor marker for melanoma. Neuron-specific enolase (choice D) and synaptophysin (choice E) are markers for neurons.Diagnosis: Melanoma, metastatic cancer