Definition/General
Introduction:
Placental villitis is the inflammatory infiltration of chorionic villi by maternal inflammatory cells
It represents a chronic inflammatory process affecting the placental parenchyma
The condition may be infectious or of unknown etiology (VUE)
It occurs in 5-15% of term placentas
Associated with adverse pregnancy outcomes.
Origin:
Results from maternal immune response to fetal antigens
Infectious agents may trigger inflammation
Autoimmune mechanisms involved in some cases
Maternal T-cell infiltration of villi
Loss of maternal-fetal tolerance.
Classification:
Classified by etiology: Infectious villitis (known pathogen)
Villitis of unknown etiology (VUE)
By pattern: Focal villitis
Multifocal villitis
Diffuse villitis
By severity: Low-grade
High-grade.
Epidemiology:
Incidence: 5-15% of term placentas
VUE comprises 90% of cases
More common in late pregnancy
Associated with IUGR (15-30%)
Recurrence rate: 10-25%.
Clinical Features
Presentation:
Often asymptomatic
IUGR (intrauterine growth restriction)
Oligohydramnios
Abnormal fetal testing
Preterm labor
Stillbirth (severe cases)
Maternal hypertension.
Symptoms:
Decreased fetal movements
Abnormal growth
Maternal symptoms often absent
Associated infections may cause fever
Preterm contractions.
Risk Factors:
Advanced maternal age
Previous pregnancy complications
Autoimmune disorders
Chronic hypertension
Diabetes mellitus
Smoking
Recurrent pregnancy loss.
Screening:
Fetal growth monitoring
Doppler studies
Biophysical profile
Maternal serology (infections)
Amniotic fluid assessment.
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Gross Description
Appearance:
Often grossly normal
Pale, firm areas in severe cases
Decreased placental weight
Areas of infarction may be present
Thickened membranes if associated chorioamnionitis.
Characteristics:
Normal external appearance usually
Cut surface may show pale areas
Firm consistency in affected areas
Associated findings: infarction, calcification.
Size Location:
Focal or diffuse involvement
Random distribution
Central areas more commonly affected
Peripheral sparing possible.
Multifocality:
Multifocal pattern common
Skip lesions
Progressive involvement
Associated with other placental pathology.
Microscopic Description
Histological Features:
Chronic inflammatory cells within villous stroma
Lymphocytes and plasma cells predominant
Histiocytes and macrophages
Villous fibrosis
Stromal collapse
Loss of capillaries.
Cellular Characteristics:
Maternal T-lymphocytes
Plasma cells
Macrophages (Hofbauer cells increased)
Few neutrophils
Syncytiotrophoblast may show damage
Stromal fibroblasts increased.
Architectural Patterns:
Expansion of villous stroma
Loss of fetal vessels
Villous sclerosis
Obliterative endarteritis
Trophoblast basement membrane thickening.
Grading Criteria:
Low-grade: <10 villi per focus
High-grade: >10 villi per focus
Basal villitis: maternal surface involvement
Obliterative endarteritis: vessel involvement
Extent assessment: focal vs diffuse.
Immunohistochemistry
Positive Markers:
CD3 (T-lymphocytes)
CD20 (B-lymphocytes)
CD68 (macrophages)
CD138 (plasma cells)
Smooth muscle actin (vessel walls)
Trichrome (fibrosis).
Negative Markers:
Cytokeratin (trophoblast - may be decreased)
CD34 (endothelium - may be lost)
Specific infectious agents usually negative.
Diagnostic Utility:
Characterizes inflammatory infiltrate
Assesses severity
Rules out infections
Demonstrates vascular involvement
Quantifies tissue damage.
Molecular Subtypes:
T-cell mediated villitis
Mixed inflammatory pattern
Obliterative villitis
Infectious villitis.
Molecular/Genetic
Genetic Mutations:
HLA associations
Complement system variants
Cytokine gene polymorphisms
FcĪ³R variants
KIR gene variations.
Molecular Markers:
Pro-inflammatory cytokines
Th1 response markers
Complement activation
Apoptosis markers
Fibrosis mediators.
Prognostic Significance:
High-grade villitis: worse outcomes
Recurrence risk in subsequent pregnancies
Associated IUGR
Increased stillbirth risk
Preterm delivery.
Therapeutic Targets:
Immunosuppressive therapy (experimental)
Antithrombotic agents
Fetal surveillance
Early delivery if indicated
Treatment of underlying conditions.
Differential Diagnosis
Similar Entities:
Acute chorioamnionitis
Chronic intervillositis
Massive perivillous fibrin
Decidual vasculopathy
Infectious placentitis.
Distinguishing Features:
Villitis: Villous inflammation
Lymphocytic infiltrate
Maternal cells
Chorioamnionitis: Membrane inflammation
Neutrophilic infiltrate
Intervillositis: Intervillous space inflammation
Perivillous fibrin.
Diagnostic Challenges:
Distinguishing infectious from non-infectious
Grading severity
Assessing clinical significance
Sampling variations
Correlation with outcomes.
Rare Variants:
Necrotizing villitis
Granulomatous villitis
Eosinophilic villitis
Giant cell villitis.
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
Placenta with chronic villous inflammation
Diagnosis
Chronic villitis [of unknown etiology/infectious]
Clinical Correlation
[IUGR/oligohydramnios/normal pregnancy]
Gross Findings
[Normal appearance/pale firm areas], weight [X] grams
Microscopic Findings
Chronic inflammatory cells within villous stroma
Villitis Grade
[Low-grade/High-grade] villitis
Distribution Pattern
[Focal/Multifocal/Diffuse] involvement
Vascular Changes
Obliterative endarteritis: [present/absent]
Associated Findings
[Infarction/fibrosis/calcification]: [present/absent]
Clinical Significance
[Mild/Moderate/Severe] based on grade and extent
Final Diagnosis
Chronic villitis of unknown etiology, [grade]