Biologic Behaviour

•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

Diagnosis

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

Clinical Staging

Treatment

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