Hemangiosarcomas confined to the skin and underlying muscle were surgi
cally excised in 25 dogs. Tumors were staged based on their histologic
al location (ie, dermal, hypodermal, and deep). Dermal (stage I) heman
giosarcomas were small, most commonly ventral-abdominal or prepucial i
n location, and were associated with prolonged survival times (median
survival, 780 days). Tumors with hypodermal (stage II) and underlying
muscular involvement (stage III) were grouped together because of thei
r larger size, bruise-like appearance, lack of anatomic predilection,
biological behavior, and shorter survival times (median survival of 17
2 and 307 days for dogs with stages II and III, respectively). We conc
lude that dermal hemangiosarcomas may be effectively treated with surg
ery alone, whereas hemangiosarcomas located within the hypodermal tiss
ues bear a poor prognosis and warrant wide surgical excision with adju
vant chemotherapy.