Congenital intrahepatic arteriovenous fistulae, a rare hepatic vascular anomaly, in an 8-mo-old female beagle dog was investigated. The animal showed anorexia, repeated vomiting, hemorrhagic diarrhea, and jaundice for approximately 2 wk. There was mild to severe increase of serum alkaline phosphatase, glutamic-oxalacetic transaminase, glutamic pyruvic transaminase, total cholesterol, total bilirubin, and γ-glutamyl transpeptidase. Macroscopically, the main abdominal organs showed hemorrhagic edema together with bloody ascites. Other characteristic findings were severe hepatic atrophy (right medial, quadrate, left medial, and lateral lobes) with multiple vascular cysts and compensatory hypertrophy of the other lobes. The cystic vessels seemed to extend from the proper hepatic arteries and their branches but were indistinguishable from the portal vein. Histopathologically, the atrophied hepatic lobes were characterized by wide, fibrous septa containing severe hyperplasia and anastomosis of the arteriolae and venulae and proliferation of bile ducts.

A spontaneous mammary adenocarcinoma was detected in a 10-wk-old female virgin Sprague-Dawley rat in a subacute toxicity study for safety assessment. The rat was sacrificed according to the study schedule at 23 wk of age and was subjected to complete necropsy. Gross pathological examination revealed that the tumor had reached 20 x 35 x 45 mm. It was settled in the right posterior abdominal subcutaneous tissue and had not invaded the surrounding tissues. Histopathologically, it was diagnosed as a typical mammary adenocarcinoma of rats. In our literature search, we found no previous reports of spontaneous adenocarcinomas of the mammary gland in such a young rat. Therefore, attention should be paid to the fact that mammary adenocarcinomas can occur spontaneously at an early age in rats.

Light microscopic, histochemical and ultrastructural observations were conducted to examine a

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