Hysteroscopic Endometrial Biopsy with Immunohistochemistry in the Diagnosis of Endometritis
Chronic endometritis (CE) is a subtle inflammatory condition of the endometrium characterized by the persistent infiltration of plasma cells within the endometrial stroma. Despite its potential association with adverse reproductive outcomes—including abnormal uterine bleeding, recurrent pregnancy loss, infertility, and repeated implantation failure—CE often presents with nonspecific or mild symptoms. The lack of universally accepted diagnostic criteria and the challenges in distinguishing plasma cells from other stromal cells under conventional staining methods contribute to underdiagnosis and variability in reported prevalence rates, which range from 8% to 72% in women of reproductive age. This study evaluates the combined use of hysteroscopic evaluation, targeted endometrial biopsy, and immunohistochemical (IHC) staining for CD138 and CD38 to improve the accuracy of CE diagnosis.
Diagnostic Challenges in Chronic Endometritis
The diagnosis of CE traditionally relies on histological identification of plasma cells in endometrial tissue samples stained with hematoxylin and eosin (H&E). However, differentiating plasma cells from stromal fibroblasts or monocytes using H&E alone is highly subjective and heavily dependent on the pathologist’s expertise. Variations in sample quality, such as inadequate tissue collection or improper fixation, further compromise diagnostic reliability. These limitations result in inconsistent detection rates and underscore the need for standardized, objective diagnostic methods.
To address these challenges, recent research has emphasized the utility of immunohistochemical markers specific to plasma cells. CD138 (a transmembrane heparan sulfate proteoglycan) and CD38 (a type II transmembrane glycoprotein) are highly specific to plasma cell membranes and cytoplasm, enabling clearer identification under microscopy. Studies suggest that IHC staining for these markers significantly reduces diagnostic subjectivity, particularly for less experienced pathologists, and improves detection rates compared to H&E staining alone.
Role of Hysteroscopy in Targeted Biopsy
Hysteroscopy has emerged as a valuable tool for the visual assessment of endometrial inflammation. The procedure allows direct visualization of endometrial features associated with CE, such as hyperemia, stromal edema, micropolyps (<1 mm vascularized protrusions), and the "strawberry aspect"—a mottled appearance caused by focal hyperemia. While the sensitivity of hysteroscopy is influenced by factors like the distension medium (e.g., saline vs. glucose) and operator expertise, it provides critical advantages in guiding targeted biopsies.
In this study, hysteroscopy was performed using a 4.5–6 mm hysteroscope with 5% glucose as the distension medium, maintaining intrauterine pressure at 80–100 mmHg. The use of glucose minimizes capillary rupture and preserves endometrial integrity, enhancing the quality of collected samples. By focusing on areas displaying inflammatory features, hysteroscopy ensures that biopsies are taken from regions most likely to harbor plasma cells, thereby improving diagnostic yield.
Study Design and Methodology
A retrospective analysis was conducted on 306 patients aged 31–48 years (mean: 37.9 ± 7.5 years) presenting with abnormal uterine bleeding (69 cases), recurrent miscarriage (128 cases), or infertility/repeated implantation failure (109 cases). Exclusion criteria included active menstruation, current reproductive tract infections, intrauterine device use, hormonal therapy within three months, pregnancy, or suspected endometrial malignancy.
Endometrial biopsies were obtained under hysteroscopic guidance and fixed in 4% neutral formaldehyde for processing. Tissue sections underwent H&E staining and IHC staining using monoclonal antibodies against CD138 and CD38 (1:100 dilution). Diagnostic criteria for CE included:
- Hysteroscopy: Presence of at least one visual feature (hyperemia, strawberry aspect, stromal edema, or micropolyps).
- H&E Pathology: Identification of ≥1 plasma cell per 10 high-power fields (HPFs).
- IHC: Brown-yellow cytoplasmic/membrane staining indicating CD138/CD38 positivity.
Statistical analysis using SPSS 20.0 assessed diagnostic concordance between hysteroscopy, H&E, and IHC via sensitivity, specificity, and Kappa values.
Key Findings and Diagnostic Performance
Hysteroscopy identified CE in 132/306 cases (43.14%), while H&E and IHC detected CE in 110 (35.95%) and 117 (38.24%) cases, respectively [Table 1]. Using H&E as the reference standard, hysteroscopy demonstrated 83.33% sensitivity and 89.91% specificity, with strong diagnostic concordance (Kappa = 0.91). IHC exhibited superior sensitivity (94.02%) and specificity (96.55%) compared to H&E, with near-perfect concordance (Kappa = 0.97).
| Table 1: Diagnostic Outcomes of Hysteroscopy, H&E, and IHC | Diagnostic Method | Positive Cases (%) | Sensitivity (%) | Specificity (%) | Kappa Value |
|---|---|---|---|---|---|
| Hysteroscopy | 132 (43.14) | 83.33 | 89.91 | 0.91 | |
| H&E Staining | 110 (35.95) | 100 | 100 | – | |
| IHC Staining | 117 (38.24) | 94.02 | 96.55 | 0.97 |
The higher detection rate of IHC (38.24% vs. 35.95% for H&E) highlights its enhanced ability to identify sparse or atypically distributed plasma cells. False-negative results in H&E staining likely stem from sampling errors or difficulty in distinguishing plasma cells in suboptimal sections. Conversely, hysteroscopy’s moderate sensitivity reflects the focal nature of CE, where inflammatory changes may be absent in biopsied areas.
Clinical Implications and Recommendations
The integration of hysteroscopy and IHC addresses key limitations in CE diagnosis. Hysteroscopy enables targeted biopsy of visually abnormal endometrium, increasing the likelihood of capturing inflammatory foci. IHC then provides an objective, reproducible method for confirming plasma cell presence, reducing reliance on subjective H&E interpretation. This combined approach is particularly valuable in populations with high CE prevalence, such as women with recurrent pregnancy loss or unexplained infertility.
Furthermore, the study underscores the importance of standardized diagnostic protocols. For instance, defining CE positivity as ≥1 plasma cell per 10 HPFs aligns with recent recommendations to avoid underdiagnosis. The use of CD138/CD38 dual staining minimizes false positives from non-plasma cell CD138 expression (e.g., epithelial cells), ensuring diagnostic accuracy.
Conclusion
Chronic endometritis remains a diagnostically elusive condition with significant reproductive implications. This study demonstrates that hysteroscopy-guided biopsy coupled with CD138/CD38 IHC staining significantly improves diagnostic precision compared to traditional H&E staining. The high concordance between IHC and H&E (Kappa = 0.97) supports the incorporation of IHC into routine practice, particularly in settings with limited access to expert pathologists. By combining endoscopic visualization, targeted tissue sampling, and molecular confirmation, clinicians can achieve earlier and more accurate CE diagnosis, facilitating timely therapeutic interventions and improving patient outcomes.
doi.org/10.1097/CM9.0000000000001275
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