Endometrium

The endometrium is typically biopsied because of abnormal bleeding.

Biopsies done for bleeding:

• Too much bleeding (if premenopausal) - AUB = abnormal uterine bleeding.
• Post-menopausal bleeding.
• Dysfunctional uterine bleeding aka DUB (follow-up).
  • DUB is diagnosed if other causes of bleeding are excluded - these patients are followed.

Micro.

• Endocervical glands are commonly seen, as is endocervical mucous.
  • This is 'cause the gynecologist scrapes some off on the way in or out.

Endocervical glands vs. Endometrial glands

Endocervical

• Less hyperchromatic.
• Nuclei round & small.
• Cell borders usually well-defined.

Endometrial

• More hyperchromatic.
• Nuclei columnar.

A simple approach

Low power

1. Decide whether you're look at endometrium.
2. Gland-to-stroma ratio normal?
   • 1:3 is normal.
   • If gland-to-stroma ratio is increased... think endometrial hyperplasia.
   • If glands are fused to one another or cribriform... think endometrial carcinoma.
3. Glands round?
   • Round is normal.
   • Irregular - may be seen in menses, endometrial hyperplasia other endometrial pathology.
4. Glands pseudostratified?
   • pseudostratified glands are normal in the proliferative phase.

High power

1. Mitoses present in the glands?
   • Present in the proliferative phase, hyperplasias, malignancies.
2. Mitoses present in the stroma?
   • Present in the proliferative phase, hyperplasias, malignancies.
3. Mucous present in the glands?
   • Present in the secretory phase.
4. Inflammatory cells present?
   • Some are normal during menses.

Endometrial polyp

Epidemiology

• Very common.

Microscopy

Features:

• Large blood vessels (muscular) - key feature.
• Fibrotic stroma - key feature.
• Polypoid shape - epithelium on three sides.
  • May not be seen... as polyp is fragmented on removal.

Notes:

• Endometrial glands may be out of phase with surrounding endometrium.
  • Often proliferative.
• +/-Cystic dilation of glands.
• Cellular stroma.

Dating endometrium

Proliferative phase

• GLANDS: straight, tubular, tall pseudostratified columnar cells, mitotic figures, NO vacuolation, NO mucus secretion.
  • Key features: pseudostratification, mitoses.
• STROMA: cellular stroma (spindle cells), mitoses.

Note:

• Proliferative phase = folicular phase.
  • Gynecologists prefer the ovarian descriptor, i.e. follicular phase; pathologists go by what they see, i.e. proliferative endometrium.

Secretory phase

• Early secretory phase - post-ovulatory day 1-5:
  • GLANDS: secretory vacuoles.
    • First basal to the epithelial nuclei (infranuclear vacuoles).
    • Then apical to the epithelial nuclei (supranuclear vacuoles).

• Mid secretory phase - post-ovulatory day 6-8:
  • GLANDS: Mucus in glands.
  • STROMA: Edema (empty space around the glands).

• Late secretory phase (begining) - post-ovulatory day 9-12:
  • STROMA: Spiral arterioles.
  • STROMA: Predecidual changes -- mnemonic NEW:
    • Nucleus central.
    • Eosinophilic cytoplasm key feature (may be subtle to the novice).
    • Well-defined cell borders.

• Premenstrual
  • STROMA: Neutrophils, scattered lymphocytes, stromal balls - "blue balls" - "stromal condensation" (Image: Endometrial stromal condensation (WC)).
  • GLANDS: Apoptosis at the base of the gland.

General refs.:

Notes:

• Secretory phase = luteal phase.
  • Gynecologists prefer the ovarian descriptor, i.e. luteal phase; pathologists go by what they see, i.e. Secretions in the (endometrial) glands.
• When the patient is >40 years, some advocate the use of the term proliferative type endometrium (instead of the term proliferative endometrium).
• Stromal condensation (stromal balls?) - premenstrual - stromal cells tightly packed together; nuclei molded together like in small cell tumours.

Abnormalities of endometrium

Anovulatory endometrium

Features:

• proliferative type endometrium BUT cystic dilation of glands without secretions
• stromal condensation -- balls of stromal tissue, aka "blue balls" (due to breakdown of endometrium)
  • PROLIFERATIVE PHASE ENDOMETRIUM
    • glands: straight, tubular, tall pseudostratified columnar cells, mitotic figures, NO vacuolation, NO mucus secretion, mitoses
    • stroma: cellular, stroma (spindle cells), mitoses

Endometrium of a woman taking OCP

Features:

• Inactive glands.
• Stroma decidualized -- mnemonic NEW:
  • Nucleus central.
  • Eosinophilic cytoplasm.
  • Well-defined cell borders.

Postmenopausal women

• If a woman is truly postmenopausal, mitoses in the glandular epithelium is pretty much always pathologic.
  • Exception is inflammation... e.g. the person has had several biopsy attempts and was seeded with pathogens.

Endometrial hyperplasia

Main article: Endometrial hyperplasia

Endometrial carcinoma

Main article: Endometrial carcinoma