Box 1.

Classification and associated features of histological examination of endometrial tissue

Unassessable

• No tissue identified
• Tissue insufficient for diagnosis
• No endometrium identified
• Endometrial tissue insufficient for diagnosis

Inactive

• Narrow tubular glands lined with cuboidal epithelium

Atrophic

• Cystically dilated glands lined by single layer of inactive, flattened epithelial cells

Proliferative

• Presence of epithelial mitoses

Secretory

• Epithelial cytoplasmic vacuolation—subnuclear or supranuclear

• Glandular luminal secretion in mid-phase and late phase

Pseudo-decidual change

• Typical stromal decidual change associated with inactive or weakly secretory glands, induced by progestogen

Simple hyperplasia

• Dilated glands with increased nuclear stratification of lining epithelium and increased stromal mitoses

• No risk of malignancy

Complex hyperplasia

• Crowded and irregular branched glands

• Low risk of malignancy

Atypical hyperplasia (intraendometrial neoplasia)

• Atypical epithelial cells; high risk of malignancy