Which of the following is NOT a form of hemangiosarcoma?

Hemangiosarcoma is a type of cancer that originates from the endothelial cells lining blood vessels and is most commonly associated with the skin, spleen, liver, and heart. The classifications of hemangiosarcoma you encounter—cutaneous, visceral, and subcutaneous—refer to the locations where these tumors can develop in animals.

Cutaneous hemangiosarcoma occurs in the skin, typically as nodular lesions that can be externally observable and may bleed or ulcerate. Visceral hemangiosarcoma arises from internal organs, with the spleen being particularly common. Subcutaneous hemangiosarcoma is found beneath the skin, similar to cutaneous, but located in deeper layers of tissue.

Endometrial tumors arise from the lining of the uterus, which is not related to hemangiosarcoma as it does not originate from blood vessels. Therefore, the endometrial designation does not fit within the known categories of hemangiosarcoma, confirming it as the correct answer in this context.

Understanding the classification of tumors is important in oncology as it dictates both prognosis and treatment options for affected animals.