In brain tumor imaging, which feature most suggests metastasis rather than a primary brain tumor?

• A. Ring-enhancing lesions with surrounding edema
• B. A single irregular enhancing lesion with infiltration
• C. Diffuse non-enhancing white matter changes
• D. Calcified nodules without edema

Answer: (A)

Metastases tend to produce multiple, well-circumscribed lesions at the gray–white matter junction with surrounding vasogenic edema. The central tumor often undergoes necrosis, leading to ring enhancement after contrast. This combination—ring-enhancing lesions with surrounding edema—is the most characteristic clue pointing toward metastatic disease rather than a primary brain tumor, which is more often solitary and infiltrative with irregular margins. Diffuse non-enhancing white matter changes suggest demyelination or age-related changes, and calcified nodules without edema are not the typical metastatic pattern.