Two cases of stereotactically induced and spontaneously metastasizing
neoplasms in the rat and the cat brain are reported. In the rat, a
malignant Schwannoma derived from initially supratentorially implanted RN6 cells developed a second
tumor in the posterior cranial fossa. In the cat, a highly malignant polymorphous anaplastic
glioma induced by implantation of cloned rat
glioma cells (F98) into the left internal capsule developed small
tumor cell nests along the ependyma of the ipsilateral ventricle. In precontrast magnetic resonance imaging (MRI) of both cases, the primary
tumor was detectable only by a very weak hypointensity and through a shift of the midline. No
metastases were apparent. Application of the metallated paramagnetic
porphyrin derivative
manganese(III) tetraphenylporphine sulfonate (
MnTPPS) resulted in a remarkable contrast enhancement between tumoral and normal tissue, which was evident not only in the primary
tumor but also in the small
metastases. These observations demonstrate for the first time that
MnTPPS is an efficient MRI
contrast agent for the detection of
metastases from
primary brain neoplasms and, in consequence, support the hypothesis of its selective binding to
tumor cells.