What are the most common primary tumors that cause hemorrhagic metastases to the central nervous system (CNS), and what are their key imaging features?

The most common primary tumors causing hemorrhagic CNS metastases are melanoma, renal cell carcinoma, thyroid carcinoma, and choriocarcinoma. On imaging, these metastases often appear hyperdense on CT due to acute hemorrhage and may show heterogeneous enhancement on MRI. Clinically, they can present with sudden neurological deficits due to bleeding. A common pitfall is mistaking these lesions for primary CNS hemorrhages; however, a history of known malignancy and the presence of multiple lesions can aid in differentiation.