Definition/General
Introduction:
Splenic peliosis is a rare vascular condition characterized by multiple blood-filled cystic spaces within the splenic parenchyma
These spaces lack true endothelial lining and represent dilatation of splenic sinusoids
Peliosis can be idiopathic or associated with various drugs, infections, or systemic conditions
The condition can mimic neoplastic processes on imaging and requires histopathologic diagnosis.
Origin:
Results from sinusoidal dilatation due to obstruction of splenic venous outflow or direct sinusoidal injury
Drug-induced cases most common, especially anabolic steroids and contraceptives
Infectious causes include Bartonella, tuberculosis
Hematologic malignancies may be associated
Exact pathogenesis often multifactorial.
Classification:
By etiology: Drug-induced (anabolic steroids, oral contraceptives)
Infection-associated (Bartonella, TB, HIV)
Malignancy-related (hematologic neoplasms)
Idiopathic
By morphology: Phlegmonous type (inflammatory)
Parenchymatous type (non-inflammatory)
By distribution: Focal
Diffuse.
Epidemiology:
Rare condition: Few hundred cases reported
Age: More common in adults, rare in children
Gender: Male predominance in anabolic steroid-related cases
Risk factors: Anabolic steroid use, immunosuppression, chronic infections
Associated conditions: HIV, hematologic malignancies, chronic liver disease.
Clinical Features
Presentation:
Asymptomatic in many patients (incidental finding)
Left upper quadrant pain when symptomatic
Splenomegaly in advanced cases
Constitutional symptoms: Fatigue, weight loss
Complications: Splenic rupture (rare but life-threatening).
Symptoms:
Abdominal symptoms: Left upper quadrant discomfort or pain
Abdominal fullness and early satiety
Systemic symptoms: Fatigue and weakness
Fever if associated with infection
Acute symptoms: Sudden severe pain (rupture)
Hemodynamic instability (internal bleeding).
Risk Factors:
Drug exposure: Anabolic steroids (most common)
Oral contraceptives
Azathioprine
Infections: Bartonella henselae
Mycobacterium tuberculosis
HIV infection
Malignancies: Lymphomas and leukemias
Chronic conditions: Chronic kidney disease, liver disease.
Screening:
High-risk patients: Those with drug exposure or predisposing conditions
Imaging studies: CT or MRI showing multiple cystic lesions
Clinical correlation: History of drug use, infections, malignancies
Laboratory studies: CBC, liver function tests, HIV testing if indicated.
Master Splenic Peliosis Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Multiple blood-filled cystic spaces of varying sizes throughout splenic parenchyma
Dark red to purple lesions resembling small lakes of blood
Spongy consistency due to multiple cavities
Size range: Few millimeters to several centimeters
Honeycomb appearance on cut surface.
Characteristics:
Cystic spaces contain dark red blood without clotting
Thin walls or absent walls around cavities
Surrounding splenic tissue may appear normal or atrophic
No true capsule around individual lesions
Confluent areas may form larger cavities.
Size Location:
Distribution: May be focal or involve entire spleen
Size variation: Multiple small lesions to large cavernous spaces
Predilection: No specific anatomic preference within spleen
Bilateral involvement of splenic lobes
Associated splenomegaly variable.
Multifocality:
Multifocal lesions typical pattern (>90% of cases)
Scattered throughout parenchyma in random distribution
Coalescence of smaller lesions into larger spaces
No associated mass lesions typically
Surrounding tissue may show reactive changes.
Microscopic Description
Histological Features:
Blood-filled spaces lacking true endothelial lining
Dilated sinusoids with absent or incomplete endothelial cells
Fibrin deposition may line some cavities
Surrounding atrophic splenic tissue
Chronic inflammation may be present.
Cellular Characteristics:
Absent endothelial lining: Key distinguishing feature from true vascular lesions
Red blood cells filling cystic spaces
Macrophages may be present around lesions
Fibroblasts in areas of organization
Inflammatory infiltrate variable depending on cause.
Architectural Patterns:
Cystic pattern: Multiple blood-filled spaces of varying sizes
Sinusoidal pattern: Dilated sinusoidal spaces
Cavernous pattern: Large confluent blood-filled cavities
Atrophic pattern: Surrounding splenic tissue shows atrophy
Inflammatory pattern: Associated inflammation in some cases.
Grading Criteria:
Mild peliosis: Few small blood-filled spaces, minimal architectural distortion
Moderate peliosis: Multiple spaces with partial architectural effacement
Severe peliosis: Extensive involvement with marked architectural distortion
Complicated peliosis: With rupture, hemorrhage, or secondary changes.
Immunohistochemistry
Positive Markers:
Factor VIII: May highlight residual endothelial cells
CD31: Positive in residual endothelial cells (often patchy or absent)
CD68: Positive in macrophages around lesions
Trichrome stain: Highlights fibrin deposition.
Negative Markers:
Consistent endothelial markers: CD31, CD34 typically absent or patchy in cyst walls
Epithelial markers: Cytokeratins negative
Smooth muscle markers: SMA negative in cyst walls
Lymphoid markers: CD45 negative in cyst walls.
Diagnostic Utility:
Exclusion of true vascular lesions: Absence of consistent endothelial lining
Demonstration of sinusoidal origin: Patchy endothelial markers
Inflammatory assessment: CD68+ macrophages
Fibrin detection: Trichrome or fibrin stains.
Molecular Subtypes:
Drug-induced type: May show specific inflammatory patterns
Infectious type: Associated inflammatory markers
Idiopathic type: Minimal inflammatory changes
Malignancy-associated: May have associated neoplastic cells.
Molecular/Genetic
Genetic Mutations:
No specific genetic mutations: Represents acquired vascular abnormality
Drug-metabolizing enzymes: Genetic variants may influence susceptibility
Angiogenesis pathway genes: May be altered in some cases
Coagulation genes: Variants may influence development.
Molecular Markers:
Angiogenic factors: VEGF expression may be altered
Inflammatory mediators: Cytokines in inflammatory cases
Endothelial dysfunction markers: Altered in affected sinusoids
Drug metabolism markers: In drug-induced cases.
Prognostic Significance:
Depends on underlying cause: Drug-induced cases have better prognosis with drug withdrawal
Extent of involvement: Diffuse involvement may have worse prognosis
Associated conditions: Malignancy-associated cases have poor prognosis
Complications: Rupture risk increases with extensive involvement.
Therapeutic Targets:
Drug withdrawal: Primary intervention in drug-induced cases
Treatment of underlying conditions: Infections, malignancies
Anti-angiogenic therapy: Theoretical approach, limited data
Supportive care: Monitoring for complications.
Differential Diagnosis
Similar Entities:
Splenic hemangioma: True vascular tumor with endothelial lining
Splenic cysts: True cysts with epithelial or mesothelial lining
Splenic abscesses: Infected cavities with purulent contents
Splenic metastases: Neoplastic lesions with different morphology
Splenic infarcts: Ischemic necrosis with different pattern.
Distinguishing Features:
Peliosis vs hemangioma: Absent vs present endothelial lining
Blood-filled vs organized vascular spaces
Peliosis vs cysts: Blood-filled vs clear/serous fluid
No epithelial lining vs epithelial lining
Peliosis vs abscess: Sterile blood vs purulent contents
Clinical correlation essential.
Diagnostic Challenges:
Imaging interpretation: May mimic neoplastic or cystic lesions
Sampling issues: May collapse during processing
Distinction from hemorrhage: Organized blood vs acute bleeding
Associated conditions: May be overshadowed by underlying disease.
Rare Variants:
Giant peliotic lesions: Very large blood-filled cavities
Calcified peliosis: Chronic cases with calcification
Infected peliosis: Secondary bacterial infection
Peliosis with rupture: Complicated by bleeding
Combined with other lesions: May coexist with tumors or infections.
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
[Biopsy/splenectomy] specimen with history of [drug exposure/underlying condition]
Gross Description
Multiple blood-filled cystic spaces measuring [size range] distributed [focally/diffusely] throughout spleen
Microscopic Findings
Blood-filled spaces lacking endothelial lining with [surrounding tissue characteristics]
Special Stains
CD31/CD34: [patchy/absent] in cyst walls. Trichrome: [fibrin deposition pattern]
Diagnosis
Splenic peliosis, [extent], likely [drug-induced/infection-related/idiopathic]
Probable Etiology
[Drug-induced/infection-associated/malignancy-related] based on clinical correlation
Complications
[Present/absent]: [rupture/hemorrhage/secondary infection]
Recommendations
[Drug withdrawal/treatment of underlying condition] and clinical monitoring for complications