Definition/General
Introduction:
Splenic cysts are fluid-filled cavities within the splenic parenchyma that can be congenital or acquired
They represent rare lesions with incidence of 0.07% in general population
Splenic cysts are classified into primary (true) cysts with epithelial lining and secondary (false) cysts without epithelial lining
Most are benign and asymptomatic but may cause complications if large.
Origin:
Primary cysts arise from developmental anomalies during embryogenesis
Mesothelial cysts develop from mesothelial inclusions
Epidermoid cysts result from ectodermal inclusion
Secondary cysts develop following trauma, infarction, infection, or hemorrhage
Parasitic cysts (hydatid) result from Echinococcus infection.
Classification:
Primary (true) cysts: Epidermoid cysts (squamous epithelium)
Mesothelial cysts (mesothelial lining)
Dermoid cysts (rare)
Secondary (false) cysts: Post-traumatic pseudocysts
Post-infarction cysts
Hemorrhagic cysts
Parasitic cysts: Hydatid cysts (Echinococcus)
Neoplastic cysts: Cystic lymphangioma.
Epidemiology:
Bimodal age distribution: Children and young adults (congenital) vs older adults (acquired)
Female predominance (3:1 ratio) in epithelial cysts
Parasitic cysts more common in endemic areas (Mediterranean, Middle East)
Size variation: From few millimeters to >20 cm
Most are asymptomatic and discovered incidentally.
Clinical Features
Presentation:
Asymptomatic in 50-70% of patients (incidental finding)
Left upper quadrant pain when large (>5 cm)
Early satiety and fullness due to gastric compression
Palpable mass in left upper quadrant
Complications: Rupture (spontaneous or traumatic), infection, hemorrhage.
Symptoms:
Abdominal symptoms: Vague left upper quadrant discomfort
Postprandial fullness and bloating
Mass effect symptoms: Early satiety, nausea
Dyspnea if very large
Acute symptoms: Sudden severe pain (rupture or hemorrhage)
Fever if infected
Systemic symptoms rare unless complicated.
Risk Factors:
Developmental factors: Congenital malformations
Family history of cystic diseases
Acquired factors: Previous splenic trauma
History of splenic infarction
Geographic factors: Endemic areas for hydatid disease
Gender: Female predominance in epithelial cysts.
Screening:
Incidental detection on routine imaging (CT, MRI, ultrasound)
Symptomatic evaluation in patients with abdominal pain
Follow-up imaging for known cysts to assess growth
Hydatid serology in endemic areas or suspicious cases
Tumor markers if malignancy suspected.
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Gross Description
Appearance:
Smooth-walled, thin-walled cystic lesion containing clear to straw-colored fluid
Unilocular in most primary cysts
Multilocular appearance in some mesothelial cysts
Thick, fibrous wall in secondary cysts
Calcification may be present in chronic cases.
Characteristics:
Size range: From few millimeters to 30 cm (average 5-10 cm)
Smooth internal surface in epithelial cysts
Trabeculated appearance in secondary cysts
Clear fluid contents in simple cysts
Turbid or hemorrhagic fluid in complicated cysts
Daughter cysts in hydatid disease.
Size Location:
Location: Any part of spleen, no specific predilection
Subcapsular location in 30-40% of cases
Central location may compress splenic vessels
Size correlation: Larger cysts more likely to be symptomatic
Growth rate generally slow (1-2 cm/year).
Multifocality:
Solitary cysts in 85-90% of cases
Multiple cysts may occur in polycystic disease
Associated findings: Other organ cysts in polycystic syndromes
Splenic atrophy around large cysts
No associated lymphadenopathy unless infected.
Microscopic Description
Histological Features:
Primary cysts: Thin fibrous wall lined by epithelium
Epidermoid cysts: Stratified squamous epithelium without adnexal structures
Mesothelial cysts: Single layer of flattened mesothelial cells
Secondary cysts: Fibrous wall without epithelial lining
Chronic inflammation may be present in wall.
Cellular Characteristics:
Epithelial lining (when present): Flattened to cuboidal cells
No significant cytologic atypia
Supporting stroma: Fibrous connective tissue
Chronic inflammatory infiltrate
Calcification and hemosiderin deposition in chronic cases
Foreign body giant cells around keratin debris.
Architectural Patterns:
Simple cystic architecture with smooth contours
Trabeculation may be present in complex cysts
Septations in multilocular cysts
Papillary projections rare (suggest malignancy)
Peripheral compressed splenic tissue around large cysts.
Grading Criteria:
Simple cysts: Thin wall, clear contents, no complications
Complex cysts: Thick wall, internal echoes, septations
Complicated cysts: Evidence of hemorrhage, infection, or rupture
Suspicious features: Solid components, papillary projections, thick irregular septations.
Immunohistochemistry
Positive Markers:
Epithelial markers (in true cysts): Pan-cytokeratin (AE1/AE3)
EMA in mesothelial cysts
Squamous markers: p63, CK5/6 in epidermoid cysts
Mesothelial markers: Calretinin, WT-1 in mesothelial cysts
Vimentin in stromal components.
Negative Markers:
Tumor markers: CEA, CA-125 typically negative (unless mucinous)
Lymphoid markers: CD45, CD20, CD3 negative
Melanoma markers: S-100, Melan-A negative
Sarcoma markers: Specific sarcoma markers negative.
Diagnostic Utility:
Confirmation of epithelial lining in primary cysts
Subtyping: Squamous vs mesothelial origin
Exclusion of malignancy: Tumor markers typically negative
Differential diagnosis: From cystic neoplasms
Assessment of wall characteristics: Inflammatory vs neoplastic.
Molecular Subtypes:
Developmental cysts: Associated with developmental gene expression patterns
Post-traumatic cysts: Inflammatory and repair markers
Mesothelial cysts: Mesothelial differentiation markers
Parasitic cysts: Host inflammatory response patterns.
Molecular/Genetic
Genetic Mutations:
Developmental genes: Associated with splenic development abnormalities
Polycystic disease genes: PKD1, PKD2 in syndromic cases
Tumor suppressor genes: Usually normal in benign cysts
Oncogenes: Typically not activated in simple cysts.
Molecular Markers:
Developmental markers: Expression of embryonic splenic development genes
Cyst formation markers: Fluid transport proteins
Membrane permeability factors
Inflammatory markers: Cytokines in complicated cysts
Repair markers: Growth factors in healing.
Prognostic Significance:
Benign nature: Simple cysts have excellent prognosis
Size progression: Slow growth rate generally
Complication risk: Increased with larger size (>5 cm)
Recurrence: Low after complete excision
Malignant transformation: Extremely rare.
Therapeutic Targets:
Conservative management: Observation for asymptomatic small cysts
Aspiration sclerotherapy: For selected cases
Surgical intervention: Cyst excision or splenectomy for large/symptomatic cysts
Minimally invasive techniques: Laparoscopic approach when possible.
Differential Diagnosis
Similar Entities:
Splenic abscess: May appear cystic but with thick enhancing wall
Splenic hematoma: History of trauma, different signal characteristics
Cystic neoplasms: Lymphangioma, cystic metastases
Parasitic cysts: Hydatid disease with daughter cysts
Pancreatic pseudocyst: May extend to spleen.
Distinguishing Features:
Cyst vs abscess: Thin vs thick wall, clear vs purulent contents, no fever vs febrile
Benign vs malignant: Simple vs complex appearance, no solid components vs nodular areas
Primary vs secondary: Epithelial lining vs fibrous wall only
Congenital vs acquired: Age at presentation, associated features.
Diagnostic Challenges:
Complex cysts: May mimic cystic neoplasms
Infected cysts: Difficult to distinguish from abscesses
Hemorrhagic cysts: May suggest malignancy on imaging
Small cysts: May be difficult to characterize
Atypical locations: May be confused with other organ cysts.
Rare Variants:
Dermoid cysts: Contain hair and sebaceous material
Bronchogenic cysts: Respiratory epithelium lining
Enterogenous cysts: Gastrointestinal epithelium
Lymphoepithelial cysts: Associated with lymphoid tissue
Endometriotic cysts: Rare splenic endometriosis.
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
[Cyst excision/splenectomy] specimen with [clinical presentation] and imaging findings of [cyst characteristics]
Gross Description
Splenic cyst measuring [dimensions] with [wall characteristics] and containing [fluid description]
Microscopic Findings
Cyst wall shows [epithelial lining present/absent] with [wall composition] and [inflammatory changes]
Special Features
[Epithelial type if present], [calcification], [hemorrhage], [inflammation] noted
Diagnosis
Splenic [cyst type]: [epidermoid/mesothelial/secondary] cyst
Classification
[Primary/secondary] splenic cyst, [simple/complex], measuring [size]
Complications
[Present/absent]: [infection/hemorrhage/rupture/none identified]
Prognosis
Benign lesion with excellent prognosis after complete excision