Definition/General
Introduction:
Splenic hemangioma is the most common benign primary tumor of the spleen, representing 0.03-14% of all splenic lesions
It is a benign vascular proliferation composed of endothelium-lined vascular spaces
Most are asymptomatic and discovered incidentally
Splenic hemangiomas are classified into capillary, cavernous, and mixed types based on vessel size and architecture.
Origin:
Believed to represent developmental vascular malformations rather than true neoplasms
Arise from abnormal proliferation of splenic vascular endothelium during embryogenesis
Cavernous type most common, composed of large dilated vascular spaces
Growth is typically slow and may remain stable for years.
Classification:
Histologic types: Cavernous hemangioma (most common 90%)
Capillary hemangioma (rare)
Mixed type
By size: Small (<2 cm)
Medium (2-5 cm)
Large (>5 cm)
Giant (>10 cm)
By number: Solitary (95%)
Multiple (rare, may suggest systemic disease).
Epidemiology:
Age distribution: Can occur at any age, peak in 30-50 years
Gender: Slight female predominance (2:1)
Incidence: Found in 0.03-14% of autopsies and CT scans
Most remain asymptomatic throughout life
Association with hemangiomas in other organs rare but reported.
Clinical Features
Presentation:
Asymptomatic in 80-90% of patients (incidental finding)
Left upper quadrant pain in symptomatic cases
Splenomegaly if tumor is large
Early satiety due to gastric compression
Thrombocytopenia due to sequestration (Kasabach-Merritt syndrome - rare).
Symptoms:
Abdominal discomfort: Vague left upper quadrant pain
Fullness after meals
Mass effect symptoms: Early satiety and bloating
Dyspnea if very large
Acute symptoms: Sudden severe pain (rupture - very rare)
Bleeding complications: Rare but potentially life-threatening.
Risk Factors:
Developmental factors: Congenital vascular malformations
Hormonal factors: Estrogen may promote growth (pregnancy, oral contraceptives)
Genetic factors: Rare familial cases reported
Other hemangiomas: May be associated with hemangiomas elsewhere.
Screening:
Incidental detection on routine imaging (CT, MRI, ultrasound)
Characteristic imaging features: Peripheral nodular enhancement
Centripetal fill-in pattern
Follow-up imaging usually not required for typical cases
Biopsy contraindicated due to bleeding risk.
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Gross Description
Appearance:
Well-circumscribed, spongy mass with dark red to purple color
Soft, compressible consistency that becomes firm after formalin fixation
Honeycomb appearance on cut surface due to vascular spaces
Smooth capsule may be present
Thrombosis and calcification in older lesions.
Characteristics:
Size range: Few millimeters to >20 cm (giant hemangiomas)
Blood-filled vascular spaces of varying sizes
Fibrous septa dividing vascular spaces
Areas of thrombosis appear as firm, gray-white zones
Calcification and fibrosis in chronic cases.
Size Location:
Location: Any part of spleen, slight predilection for subcapsular areas
Size correlation with symptoms: >5 cm more likely symptomatic
Giant hemangiomas (>10 cm) may cause significant mass effect
Multiple lesions rare (<5% of cases).
Multifocality:
Solitary lesions in 95% of cases
Multiple hemangiomas rare, may suggest systemic vascular malformation syndrome
Associated findings: Rarely associated with hemangiomas in liver or other organs
No associated lymphadenopathy
Surrounding spleen typically normal.
Microscopic Description
Histological Features:
Cavernous type: Large, dilated vascular spaces lined by flattened endothelium
Capillary type: Small, closely packed capillary-sized vessels
Fibrous septa separating vascular channels
Smooth muscle in vessel walls
Thrombosis and organization may be present.
Cellular Characteristics:
Endothelial cells: Single layer of flattened, bland endothelial cells
No cytologic atypia or mitotic activity
Supporting cells: Smooth muscle cells in vessel walls
Fibroblasts in septal areas
Blood contents: Red blood cells filling vascular spaces
Thrombi may show organization.
Architectural Patterns:
Cavernous pattern: Large, irregular vascular spaces
Capillary pattern: Small, uniform capillary-sized vessels
Mixed pattern: Combination of large and small vessels
Septal arrangement: Fibrous septa with smooth muscle
Sclerotic areas in older lesions.
Grading Criteria:
Simple hemangiomas: Typical vascular morphology, no complications
Sclerosed hemangiomas: Extensive fibrosis and hyalinization
Thrombosed hemangiomas: Organized thrombi, calcification
No malignant potential: Benign lesions with no risk of malignant transformation.
Immunohistochemistry
Positive Markers:
Endothelial markers: CD31 (strongly positive)
CD34 (strongly positive)
Factor VIII (variable)
Vascular markers: ERG (endothelial marker)
FLI-1 (endothelial marker)
Smooth muscle markers: SMA in vessel walls
Proliferation markers: Ki-67 typically very low (<1%).
Negative Markers:
Epithelial markers: Cytokeratins negative
EMA negative
Lymphoid markers: CD45 negative
Melanoma markers: S-100 negative (except in nerve fibers)
Melan-A negative
Sarcoma markers: Specific sarcoma markers negative.
Diagnostic Utility:
Confirmation of vascular nature: Endothelial markers strongly positive
Benign characteristics: Low proliferation index, typical morphology
Differential diagnosis: From other vascular lesions and tumors
Exclusion of malignancy: Angiosarcoma markers and morphology different.
Molecular Subtypes:
Cavernous hemangiomas: Mature endothelial phenotype
Capillary hemangiomas: More active endothelial markers
Sclerosed hemangiomas: Reduced vascular markers, increased fibrous markers
Infantile hemangiomas: GLUT-1 positive (rare in spleen).
Molecular/Genetic
Genetic Mutations:
Somatic mutations: TEK (TIE2) mutations in some cases
GNAQ mutations in some vascular malformations
Developmental genes: Alterations in angiogenesis pathways
Hereditary forms: Rare, associated with multiple hemangioma syndromes.
Molecular Markers:
Angiogenesis markers: VEGF expression variable
Angiopoietin-Tie2 pathway markers
Endothelial function markers: Nitric oxide synthase
von Willebrand factor
Matrix markers: Basement membrane proteins
Collagen types in septa.
Prognostic Significance:
Excellent prognosis: Benign lesions with no malignant potential
Size-related complications: Larger lesions more prone to complications
Spontaneous regression: Rare, may occur with thrombosis and fibrosis
Stability: Most remain stable in size over time.
Therapeutic Targets:
Conservative management: Observation for asymptomatic lesions
Surgical intervention: For symptomatic large lesions
Minimally invasive options: Embolization for selected cases
Spleen preservation: Enucleation when possible vs splenectomy.
Differential Diagnosis
Similar Entities:
Splenic angiosarcoma: Malignant vascular tumor with different morphology
Littoral cell angioma: Different morphology and immunoprofile
Splenic cysts: Cystic lesions without vascular nature
Splenic metastases: From vascular tumors like angiosarcoma
Peliosis: Blood-filled spaces but different architecture.
Distinguishing Features:
Hemangioma vs angiosarcoma: Benign endothelium vs atypical cells
No mitoses vs increased mitoses
Hemangioma vs littoral cell angioma: Different immunoprofile (CD68 negative vs positive)
Hemangioma vs cyst: Vascular spaces vs cystic cavity
Size and imaging characteristics help differentiation.
Diagnostic Challenges:
Sclerosed hemangiomas: May be difficult to recognize as vascular
Small lesions: May require immunohistochemistry for confirmation
Thrombosed areas: May obscure vascular nature
Biopsy interpretation: Small samples may not be representative.
Rare Variants:
Epithelioid hemangioma: Epithelioid endothelial cells
Papillary endothelial hyperplasia: Reactive endothelial proliferation
Anastomosing hemangioma: Irregular vascular pattern
Microvenular hemangioma: Small venular pattern
Hobnail hemangioma: Characteristic endothelial morphology.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[Enucleation/splenectomy] specimen with imaging findings of [vascular lesion characteristics]
Gross Description
Well-circumscribed vascular lesion measuring [dimensions] with [spongy consistency] and [honeycomb cut surface]
Microscopic Findings
[Cavernous/capillary] vascular spaces lined by [bland endothelium] with [supporting stroma characteristics]
Immunohistochemical Studies
Endothelial cells positive for CD31, CD34, and ERG. Ki-67 proliferation index <1%
Diagnosis
Splenic [cavernous/capillary] hemangioma, measuring [size]
Classification
Benign vascular tumor with no malignant potential
Complications
[Present/absent]: [thrombosis/fibrosis/calcification/none identified]
Prognosis
Excellent prognosis. Benign lesion with no risk of malignant transformation