Diagnosing endometrial hyperplasia: why is it so difficult to agree?

Area of Science:

• Gynecologic Pathology
• Histopathology
• Oncology

Background:

• The current World Health Organization (WHO) classification of endometrial hyperplasia faces challenges due to poor diagnostic reproducibility among pathologists.
• This variability can lead to inconsistent patient management and treatment decisions.

Purpose of the Study:

• To identify specific factors contributing to diagnostic disagreements in the classification of endometrial hyperplasia.
• To assess the impact of sample adequacy and histological features on inter-observer agreement.

Main Methods:

• A review of 2601 endometrial specimens was conducted, including normal endometrium, hyperplasias, and carcinoma.
• Specimens were independently reviewed by two pathologists, with a third pathologist resolving disagreements.
• Histological features such as glandular crowding, architectural complexity, cytologic atypia, sample adequacy, and hyperplasia volume were scored.

Main Results:

• Overall kappa for agreement was 0.71, but significantly lower (0.36) when 'no hyperplasia' cases were excluded.
• Specific agreement varied widely: 90.3% for no hyperplasia, 31.1% for simple hyperplasia, 51.1% for complex hyperplasia, 49.8% for atypical hyperplasia, and 57.5% for adenocarcinoma.
• Diagnostic disagreement was higher in low-volume ('scant') specimens and strongly associated with cytologic atypia, architectural crowding, architectural complexity, and the presence of an endometrial polyp.

Conclusions:

• High diagnostic disagreement in endometrial hyperplasia is linked to both sample adequacy and the interpretation of histological features.
• While obtaining more tissue may improve reproducibility, differences in interpreting critical features like cytologic atypia remain a primary cause of diagnostic variability.