+ Pathogenesis

  • HSA is a malignant neoplasm arising from endothelial cells
  • Dermal HSA accounts for 14% of primary HSA
  • Vascular stasis, radiation therapy, trauma, and sun exposure are predisposing factors in humans
  • HSA has been experimentally induced in dogs with UV radiation and solar radiation may be involved in spontaneous development of cutaneous HSA in dogs

+ Signalment

  • Sex predisposition: male
  • Breed predisposition: GSD, Boxer, Whippet, and Pit Bull Terrier
  • Dermal HSA is usually rapidly growing solitary, poorly circumscribed mass with early ulceration and infiltration
  • ≥ 1 cutaneous HSA may represent metastatic disease
  • However, multicentricity is a feature of canine HSA with up to 18% of primary cutaneous HSA presenting with multiple lesions

+ Diagnosis

  • Hemostatic disorders are common and coagulation profile and bleeding times should be assessed
  • Staging is important to assess whether cutaneous lesions are primary or metastatic lesions from a primary HSA in the spleen, right auricle, or liver

+ Clinical Stage

  • Clinical staging is based on location within the dermis or association with the dermis:
  • Stage I: dermal
  • Stage II: hypodermal
  • Stage III: muscle

+ Treatment

  • Wide surgical resection for stage I HSA
  • Wide surgical resection (i.e., limb amputation) and adjunctive chemotherapy (i.e., doxorubicin, cyclophosphamide, and vincristine) for stage II and III HSA
  • Radiation therapy is ineffective

+ Prognosis

  • Prognosis is guarded
  • 30% metastatic rate and MST 780 days for stage I HSA
  • 10% metastatic rate and MST 172 days for stage II HSA
  • 60% metastatic rate and MST 307 days for stage III HSA
  • MST for hypodermal HSA following surgery and chemotherapy: 425 days
  • Good prognostic factors in humans include small tumor size (< 5 cm) and lymphocytic infiltration around tumor


  • No breed or sex predilection
  • Gross appearance: solitary, well circumscribed, unencapsulated, red-to-black colour, and located in subcutaneous and dermoepidermal tissue


T0 No evidence of neoplasia
T1 Tumor less tbaan 5 cm in diameter and confined to primary site - Primary Tumor
T2 Tumor ≥ 5 cm in diameter, ruptured, or invading subcutaneous tissue
T3 Tumor invading adjacent structures including muscle
M0 No evidence of metastasis
M1 Evidence of distant metastasis with site specified - Metastasis
N0 No evidence of lymph node involvement
N1 Regional lymph node involvement - Node
N2 Distant lymph node involvement

Clinical Stage

I II III T T1 T1-2 T2-3 N N0 N0-1 N1-2 M M0 M1 M2