+ Biologic Behavior

  • HSA is a highly metastatic tumor with microscopic or macroscopic metastatic disease at diagnosis
  • HSA arises from vascular endothelial cells
  • HSA is the 4th most common splenic tumor in cats
  • Median age 8-10 years
  • Sex predisposition: males
  • No breed predisposition
  • Splenic HSA is highly metastatic (60%) with sites including lungs, liver, regional lymph node, mesentery, and brain

+ Clinical Signs

  • Non-specific
  • Acute Presentation: acute dyspnea, pallor, abdominal effusion, and hypovolemic shock secondary to splenic rupture and hemorrhage
  • Chronic Presentation: lethargy, anorexia, and weight loss

+ Physical Examination

  • Palpable abdominal mass with splenomegaly and abdominal fluid wave
  • Cardiac abnormalities: arrhythmia, cardiac murmur, and muffled heart sounds


+ General Considerations

Splenic HSA and hemangioma have similar ultrasonographic and gross appearance and are difficult to differentiate

+ Laboratory Findings

  • Hematology: anemia and morphological changes to red blood cells such as nucleated erythrocytes, polychromasia, poikilocytes, anisocytes, shistocytes, and reticulocytes
  • Morphologic changes due to iron loss, altered hepatic lipoprotein metabolism, microangiopathic disease, or DIC and sluggish flow through abnormal vascular channels resulting in increased membrane fragility
  • Neutrophilic leukocytosis is common due to either stress or tumor rupture and necrosis
  • Thrombocytopenia due to DIC, but may form part of Kasabach-Merritt syndrome
  • Kasabach-Merritt syndrome is characterized by an enlarging vascular tumor, thrombocytopenia, anemia, prolonged PT and APTT, decreased FDP, and increased fibrin split products
  • Thrombocytopenia (75%-90%), fragmented red blood cells (80%), and DIC (50%) are common findings
  • Anemia and DIC associated with blood loss is common in cats with visceral HSA

+ Survey Radiographs

  • 2 metastatic patterns in dogs with HSA:
  • Widely disseminated nodular pattern (common)
  • Diffuse interstitial pattern (uncommon)
  • False-negative results are high: 22% from splenic HSA and > 50% for right atrial HSA

+ Ultrasonography

  • Abdominal ultrasonography is a highly accurate and sensitive tool for splenic evaluation
  • Primary HSA: mixed pattern of anechoic and hyperechoic regions
  • Metastatic HSA: diffusely anechoic or hypoechoic appearance
  • Ultrasound-guided FNA or needle-core biopsy contraindicated due to risk of seeding and low diagnostic yield

+ Electrocardiography

Ventricular arrhythmias are commonly associated with HSA due to hypoxia, anemia, or hypovolemia


+ Surgical Management

  • Total splenectomy recommended

+ Chemotherapy

  • Doxorubicin 30 mg/m2 q 2-3 weeks for 5 doses
  • ± cyclophosphamide 100-150 mg/m2
  • Complications: neutropenia (common), severe gastroenteritis, cardiotoxicity, and sepsis

+ Prognosis

  • Mean ST 22 weeks
  • 100% metastatic rate



T0 No evidence of neoplasia
T1 Tumor less than 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 regional lymph node involvement
N1 Regional lymph node involvement - Node
N2 Distant lymph node involvement