Question ... Can you share your thoughts on why the benign version (of hemangiosarcoma) might involve many small growths on the skin and, in the words of our vet, "appear malignant?" What can we watch for that would indicate a benign growth is becoming malignant?
Answered by Douglas H. Thamm, VMD, DACVIM (Oncology):
There is no accurate way to distinguish between malignant and benign growths without a biopsy. Some dogs with the cutaneous form of hemangiosarcoma can even have a mixture of benign and malignant growths in the same area! If possible, removal of all growths with submission for histopathology is the safest course of action.
