Brain metastasis from colon cancer. Case report showing a clinical and CT unusual appearance.

The authors report the case of a patient harbouring a parietal convexity tumor whose clinical and CT features were suggestive of a meningioma. Unexpectedly the tumor was a well differentiated adenocarcinoma from a colon cancer with a markedly PAS positive intragland content represented by wide areas of mucoid degeneration. Brain metastases from colon cancer are usually late occurrences and it is extremely rare that the brain lesion be discovered while the primary tumor is still unknown. The authors discuss about the pathogenesis of the CT appearance of adenocarcinoma which is, usually, slightly hyperdense. On the basis of the reported findings it is suggested that mucoid degeneration may induce the development of a well defined CT pattern represented by a very high density appearance with no contrast enhancement.