Definition/General
Introduction:
Circummarginate placenta is characterized by flat transition zone at placental margin
It shows opaque ring on fetal surface without membrane folding
It represents extrachorial placentation
It has better prognosis than circumvallate placenta.
Origin:
Results from differential growth between chorionic and basal plates
Mild discrepancy in placental development
Gradual membrane insertion
Less severe than circumvallate
Developmental variant.
Classification:
Classified as extrachorial placenta
Complete: Entire margin involved
Partial: Portion of margin affected
Mild form of extrachorial placentation
Distinguished from circumvallate.
Epidemiology:
More common than circumvallate
Incidence approximately 5-7% of pregnancies
Usually asymptomatic
Better outcomes than circumvallate
Often incidental finding.
Clinical Features
Presentation:
Usually asymptomatic
May have mild antepartum bleeding
Better outcomes than circumvallate
Rarely associated with preterm labor
Incidental finding at delivery.
Symptoms:
No specific symptoms
Occasional light bleeding
Normal pregnancy course typically
No increased pain
Normal fetal growth usually.
Risk Factors:
Similar to circumvallate but milder associations
Advanced maternal age
Multiple pregnancy
Oligohydramnios (less common)
Uterine abnormalities.
Screening:
Routine prenatal care usually sufficient
Standard ultrasound
No special monitoring required
Normal fetal surveillance.
Master Circummarginate Placenta Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Flat opaque ring on fetal surface
No membrane folding
Smooth transition at margin
Whitish discoloration
No raised ridge
Flat appearance.
Characteristics:
Opaque white ring
Flat transition zone
No membrane doubling
Smooth surface
Less fibrous than circumvallate
Minimal hemorrhage.
Size Location:
Located at placental margin
May be complete or partial
Concentric pattern
Flat morphology
No inward folding.
Multifocality:
Circumferential involvement common
May be segmental
Uniform appearance
No skip lesions
Symmetric distribution.
Microscopic Description
Histological Features:
Flat membrane insertion
Minimal fibrous tissue
No membrane folding
Mild chronic changes
Preserved membrane architecture
Less hemorrhage than circumvallate.
Cellular Characteristics:
Minimal fibroblastic proliferation
Few inflammatory cells
Normal membrane structure predominantly
Mild chronic changes
Less hemosiderin than circumvallate.
Architectural Patterns:
Flat transition zone
Single membrane layer
No infolding
Preserved architecture
Minimal distortion
Smooth interface.
Grading Criteria:
Mild: Minimal changes, flat transition
Moderate: More obvious ring, mild fibrosis
Based on extent of opaque ring.
Immunohistochemistry
Positive Markers:
Smooth muscle actin (minimal)
CD68 (few macrophages)
Collagen stains
Factor VIII (preserved vessels)
Normal membrane markers.
Negative Markers:
Extensive fibrosis markers
Heavy inflammatory infiltrate
Acute phase reactants
Necrosis markers.
Diagnostic Utility:
Confirms minimal pathology
Distinguishes from circumvallate
Shows preserved architecture
Rules out inflammation.
Molecular Subtypes:
Not applicable for routine classification.
Molecular/Genetic
Genetic Mutations:
No specific mutations
Developmental variant
Multifactorial inheritance
No chromosomal associations typically.
Molecular Markers:
Normal growth factors
Minimal fibrosis markers
Preserved angiogenesis
Normal matrix proteins.
Prognostic Significance:
Excellent prognosis
No increased complications
Normal pregnancy outcomes
No increased mortality.
Therapeutic Targets:
No specific treatment required
Routine prenatal care
Normal delivery management
No special precautions.
Differential Diagnosis
Similar Entities:
Circumvallate placenta (membrane folding)
Normal placenta
Marginal insertion abnormalities
Placental infarcts.
Distinguishing Features:
Circummarginate: Flat transition, no folding
Circumvallate: Membrane folding, raised ridge
Normal: No opaque ring.
Diagnostic Challenges:
Subtle findings
May be missed
Clinical correlation usually normal
Distinguishing from normal variants.
Rare Variants:
Partial circummarginate
Combined with other anomalies
Extensive form.
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 showing flat opaque ring at [complete/partial] margin without membrane folding
Diagnosis
Circummarginate Placenta
Classification
Classification: [Complete/Partial] circummarginate placenta with minimal pathological changes
Morphological Features
Shows flat opaque ring without membrane folding or raised ridge formation
Histological Features
Shows minimal changes with preserved membrane architecture and no significant pathology
Clinical Significance
Benign morphological variant with excellent prognosis and no increased complications
Final Diagnosis
Circummarginate Placenta, [extent], benign variant with normal clinical significance