Perfusion MR imaging of an intracranial collision tumor confirmed by image-guided biopsy.

We present a patient with a new intracranial mass lesion that was initially interpreted as a metastasis on conventional anatomic MR imaging. On dynamic, contrast-enhanced, susceptibility-weighted perfusion MR imaging, however, there were regional hemodynamic differences within the lesion. Image-guided open biopsy targeting these regions uncovered a collision tumor between a typical meningioma and a metastatic breast carcinoma. In cases where conventional anatomic MR imaging is ambiguous, physiology-based neuroimaging methods provide complementary physiologic information useful for discriminating between histologically unique tissue types.