A 15-year-old female mongrel dog showed abdominal swelling, marked hemorrhagic ascites and vulvar discharge, and ovariohysterectomy was performed. Grossly, the uterus was enlarged bilaterally without apparent mass formation. Histologically, the uterine muscular wall was composed of proliferated sinusoidal vessels. In some areas, irregular and small vessels proliferated markedly, while in others, pleomorphic and atypical tumor cells forming irregular vascular structures were predominant. From

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... se findings, the case was diagnosed as diffuse bilateral hemangiosarcoma of the uterus that invaded to the ovary and broad ligament. The relationship between the tumor and angiomatosis was discussed.