Definition/General
Introduction:
Placental increta is characterized by invasion of chorionic villi into the myometrium
It represents the intermediate severity within the accreta spectrum disorders
The trophoblast penetrates deeply into the uterine muscle
It occurs in 15-17% of accreta spectrum cases
It poses significant risk for hemorrhage and hysterectomy.
Origin:
Results from excessive trophoblast invasion beyond normal boundaries
Associated with deficient decidua basalis
Previous uterine trauma creates susceptible areas
Abnormal placentation allows deeper penetration
Matrix metalloproteinase dysregulation may contribute.
Classification:
Part of accreta spectrum: Grade 1: Accreta vera (surface attachment)
Grade 2: Increta (myometrial invasion)
Grade 3: Percreta (full-thickness penetration)
Classification by invasion depth
May be focal or diffuse.
Epidemiology:
Comprises 15-17% of accreta spectrum disorders
Less common than accreta vera
More severe than simple accreta
Risk factors similar to other accreta types
Higher morbidity than accreta vera.
Clinical Features
Presentation:
Severe postpartum hemorrhage
Retained placenta with failed manual removal
Hemodynamic instability
DIC (disseminated intravascular coagulation)
Need for blood transfusion
Surgical intervention required.
Symptoms:
Profuse bleeding after delivery
Inability to remove placenta manually
Continued hemorrhage despite uterotonics
Shock symptoms
Abdominal pain
Oliguria from blood loss.
Risk Factors:
Previous cesarean section (major risk)
Placenta previa
Advanced maternal age
Multiparity
Previous D&C
Endometrial ablation
Asherman syndrome
Smoking.
Screening:
Prenatal MRI superior to ultrasound
Loss of T2 dark line (uterine serosa)
Myometrial thinning
Focal bulging
Abnormal vascularity
Multidisciplinary planning essential.
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Gross Description
Appearance:
Deep invasion of placental tissue into myometrium
Myometrial bundles interspersed with placental villi
No clear cleavage plane
Hemorrhagic, friable tissue
Distorted uterine architecture.
Characteristics:
Irregular, nodular areas of invasion
Myometrial fiber disruption
Vascular engorgement
Fibrous tissue proliferation
Areas of necrosis possible.
Size Location:
Invasion depth variable (few mm to several cm)
Commonly in lower uterine segment
Anterior wall frequent with cesarean scars
May be multifocal.
Multifocality:
Skip areas of invasion
Different depths in various locations
Progressive extension possible
Associated with other placental abnormalities.
Microscopic Description
Histological Features:
Chorionic villi deeply embedded in myometrium
Extravillous trophoblast invasion between muscle bundles
Myometrial fiber separation and atrophy
Chronic inflammation
Fibrous tissue replacement.
Cellular Characteristics:
Intermediate trophoblast infiltration
Syncytiotrophoblast within muscle fibers
Trophoblast giant cells
Myometrial cell degeneration
Inflammatory cell infiltration.
Architectural Patterns:
Disrupted myometrial architecture
Villous tissue replacing muscle
Irregular invasion pattern
Vascular proliferation
Fibrous septa formation.
Grading Criteria:
Depth of invasion into myometrium
Percentage of myometrial thickness involved
Extent of surface involvement
Associated vascular changes
Degree of architectural disruption.
Immunohistochemistry
Positive Markers:
Cytokeratin (trophoblast identification)
Mel-CAM (extravillous trophoblast)
Inhibin-α (trophoblast)
p63 (cytotrophoblast)
Smooth muscle actin (myometrium)
CD68 (macrophages).
Negative Markers:
Desmin (decreased in invaded myometrium)
Caldesmon (smooth muscle)
CD45 (lymphocytes)
Normal decidual markers absent.
Diagnostic Utility:
Demonstrates invasion depth
Distinguishes trophoblast from other cells
Maps extent of myometrial involvement
Useful for grading severity
Guides surgical planning.
Molecular Subtypes:
Focal increta (limited areas)
Diffuse increta (extensive)
Superficial increta (minimal depth)
Deep increta (approaching serosa).
Molecular/Genetic
Genetic Mutations:
PTEN pathway alterations
WNT signaling abnormalities
Matrix metalloproteinase dysregulation
Integrin expression changes
E-cadherin downregulation.
Molecular Markers:
Increased MMP-2, MMP-9
Decreased TIMP-1 (tissue inhibitor)
Altered VEGF expression
Abnormal integrin α1
Reduced PTEN expression.
Prognostic Significance:
Higher morbidity than accreta vera
Increased hysterectomy risk
Greater blood loss
ICU admission more likely
Future pregnancy risks.
Therapeutic Targets:
Uterine artery embolization
Balloon occlusion
Conservative surgery (selected cases)
Hysterectomy often required
Multidisciplinary management.
Differential Diagnosis
Similar Entities:
Placental accreta (surface only)
Placental percreta (full thickness)
Adenomyosis
Leiomyoma
Endometrial carcinoma invasion.
Distinguishing Features:
Increta: Partial myometrial invasion
No serosal involvement
Accreta: Surface attachment only
Percreta: Full-thickness invasion
Serosal penetration
Adenomyosis: Benign endometrial glands.
Diagnostic Challenges:
Distinguishing from percreta
Assessing invasion depth
Intraoperative recognition
Frozen section limitations
Clinical correlation needed.
Rare Variants:
Focal deep increta
Multifocal skip lesions
Associated with uterine anomalies
Coexistent adenomyosis.
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
[Hysterectomy/Partial resection] specimen with placental increta
Diagnosis
Placental increta with myometrial invasion
Clinical History
Postpartum hemorrhage, retained placenta, [risk factors]
Gross Findings
Deep placental invasion into myometrium, no clear cleavage plane
Microscopic Findings
Chorionic villi and trophoblast deep within myometrial bundles
Invasion Depth
Trophoblast invasion [X] mm into myometrium ([X]% thickness)
Extent of Involvement
[Focal/Diffuse] involvement over [X] cm area
Myometrial Changes
Muscle fiber separation, atrophy, chronic inflammation
Associated Complications
Hemorrhage, [other complications]
Final Diagnosis
Placental increta, [focal/diffuse]