Spontaneous metastasizing mucinous adenocarcinoma in the ileum of a Sprague-Dawley rat.

Spontaneous tumours of the rat small intestine are extremely rare. A control Sprague-Dawley male rat from a carcinogenicity bioassay had a mucinous adenocarcinoma in the ileum. Tumour metastasis was observed in the mesenteric lymph node, lung, and seminal vesicles. Gross and histopathological features of this neoplasm are described and discussed.