Can chronic inflammatory cells be present in the myometrium?

Chronic Inflammatory Cells in the Myometrium

Yes, chronic inflammatory cells can be present in the myometrium in both normal and pathological conditions, with their presence often indicating underlying pathological processes such as placenta accreta spectrum disorders, chronic endometritis, or other inflammatory conditions.

Normal vs. Pathological Inflammatory Presence

Chronic inflammatory cells in the myometrium typically represent a pathological finding rather than a normal occurrence. According to expert guidelines, their presence should prompt further investigation:

• In normal pregnancies, myometrial inflammatory lesions are detected rarely before parturition, indicating their abnormality in these cases 1
• When present, chronic inflammation in the myometrium often indicates an underlying pathological process

Pathological Conditions Associated with Myometrial Inflammation

1. Placenta Accreta Spectrum (PAS) Disorders

Chronic inflammation is a common histological finding in PAS:

• Most cases of PAS show overlapping features of tissue injury with degenerated myofibers, interstitial edema, and chronic inflammation 2
• In PAS with invasion, infiltrative invasion with fibrosis replacing myofibers is accompanied by increased chronic inflammation and edema 2
• The normal contour of the uteroplacental interface is lost in more extensive PAS, and chronic inflammation in the myometrium with edema and myocyte injury becomes prominent 2

2. Inflammatory Conditions

Several inflammatory conditions can lead to chronic inflammatory cell infiltration in the myometrium:

• Xanthogranulomatous inflammation can infiltrate into the uterine myometrium from the perimetrium (outer serosal layer of the uterus) 3
• Chronic inflammation may enhance leiomyoma development through the involvement of progenitor cells 4
• Monocytes play a role in modulating myometrial inflammation during human labor 5

Types of Inflammatory Cells

Different types of chronic inflammatory cells may be present in the myometrium:

• Plasma cells: Primary marker for chronic endometritis but can extend into the myometrium 6
• Eosinophils: Can be identified by their characteristic eosinophilic granules and may indicate chronic inflammation 6
• Monocytes/Macrophages: Play a role in modulating myometrial inflammation, particularly during labor 5
• Lymphocytes: Part of the chronic inflammatory response

Clinical Significance

The presence of chronic inflammatory cells in the myometrium has important clinical implications:

• In PAS disorders, chronic inflammation is part of the diagnostic criteria and helps grade the severity of the condition 2
• Chronic inflammation may contribute to adverse obstetric outcomes in women with leiomyomas, including infertility, spontaneous miscarriage, and preterm birth 4
• During labor, inflammatory cells infiltrate the myometrium after ruptured fetal membranes with advanced cervical dilatation 1

Diagnostic Approach

When chronic inflammatory cells are identified in the myometrium:

1. Determine the type and distribution of inflammatory cells
2. Assess for associated histological changes (fibrosis, edema, myocyte injury)
3. Consider the clinical context (pregnancy, previous cesarean delivery, symptoms)
4. In cases of suspected PAS, evaluate for loss of decidual layer, which is the defining histologic feature 2
5. Look for other associated findings such as vascular changes, trophoblastic invasion, or tissue destruction

Pitfalls and Caveats

• The mere presence of inflammatory cells does not establish a specific diagnosis; clinical correlation is essential
• Some conditions can mimic inflammatory cells (plasmacytoid stromal cells, predecidual changes)
• Immunohistochemistry may be needed to confirm the identity of specific inflammatory cells (e.g., CD138 for plasma cells) 6
• Moderate to marked myometrial inflammation shows no diagnostic value in high-risk term parturients for the prediction of postoperative endometritis 1

In summary, while chronic inflammatory cells can be present in the myometrium, their presence typically indicates an underlying pathological process that warrants further investigation to determine the specific etiology and appropriate management.