Intraventricular metastases is a very rare finding.
Few intracranial tumors metastasese to ventricles . Some extra cranial tumors also metastasize to ventricles . Most common site of intraventricular metastases is trigone of lateral ventricles due to high vascular supply of choroid plexus. Next common sites are 4th and 3rd ventricles.
renal cell carcinoma - most common primary
melanoma
breast carcinoma
lung carcinoma- overall most common metastases in the choroid plexus (as it is the most common tumour)