HISTOLOGY OF PHASES OF MENSTRUAL CYCLE

1. DR. MANJULA N MBBS, MD
(PATHOLOGY)

2. The endometrium and myometrium are of mesodermal origin.
Fusion of paramesonephric ducts occurs betweeen 8th & 9th
postovulatory weeks.
 20th week – Endometrium consists of single layer of columnar
epithelium with thick layer of fibroblastic stroma.

3.  After 20 weeks :
- Surface epithelium invaginates into the underlying stroma.
- Glandular strucutres are formed.
 At birth :
- ET measures 0.5 mm.
- Surface and glands – Low columnar to cuboidal epithelium.
 Prepuberty : Endometrium is inactive.
 Reproductive period :
2 layers - Stratum functionalis and stratum basalis

5. 1. Early proliferative endometrium
2. 16 day endomterium
3. Early secretory endometrium
4. Mid secretory endometrium
5. Late secretory endometrium
6. Menstrual endometrium

6. In this stage, levels of circulating estrogen increases.
Endometrial glands and stroma undergo active proliferation.

7.  Glandular
compartment evenly
distributed.
 Composed of
uniformly sized round
to tubular glands.

8. Glands are lined by columnar epithelium with
smooth apical borders with round to elongated
hyperchromatic nuclei

9.  Glandular epithelium
displays
 Nuclear elongation,
 Pseudostratification,
 Conspicuous mitotes.
 Glandular “telescoping”
artifact is frequent seen

11.  Stromal cells are uniform
and round or spindled

12.  Stroma is densely
cellular to mildly
edematous.
 Lack of prominent
spiral arterioles

13. Day 16 - when ovulation occurs.
Periovulatory endometrium is characterized by
Gland tortuosity suggesting secretory endometrium (at low
power magnification)
Focal and discontinuous subnuclear vacuolization involving less
than 50% of the cells in each gland
Readily identifiable mitotic figures

14. Day 16 (periovulatory) endometrium, variable subnuclear epithelial
vacuolization is observed, usually discontinuous and patchy. In addition, mitotic
figures are readily identified.

15. Key feature: Glandular vacuolization
Day 17: Diffuse subnuclear vacuolization in > 50% of cells in each gland
(piano key pattern); mitoses are rare to absent
Day 18: Sub- and supranuclear vacuoles; subtle apical discharge, nuclei
typically in midportion of cytoplasm
Day 19: Mostly supranuclear vacuoles and appearance of intraluminal
secretions; basal nuclei; no mitotic activity
During the early secretory phase, endometrial glands progressively
increase in size and tortuosity
As the glandular compartment grows, its relative proportion of surface
area increases (exceeding the gland to stroma ratio of 1:1 seen in the
proliferative phase)

16. Day 17 - Epithelial
vacuolization
becomes uniform
and diffuse

17. Day 18 -
Progressive
migration of the
vacuoles to
a supranuclear
location.

18. Day 19 - predominant supranuclear vacuolization.
Stroma is dense and uniform.

19. Extrusion of secretory contents into the glandular lumen. The
amount of intraluminal secretions peaks at day 20 of the cycle.
 Stromal edema is focal by day 21 and more prominent by day 22.
 Predecidual change, scanty cytoplasm- naked small nuclei,
condensed chromatin.
Day 22 the spiral arteries become more prominent and are
surrounded by stromal cells with a cuffing pattern.

20. Peak of intraluminal secretions

21. Stroma shows diffuse edema with extracellular fluid
accumulation, stromal cells separate and appear as cuffs around
spiral arterioles

22. Hallmark : Predecidual change – appearance of stromal cytologic
changes under the effect of circulating progesterone.
 Predecidualized stromal cells have a polygonal shape, abundant
basophilic cytoplasm, round nuclei with fine chromatin pattern.
 Day 23 - predecidual change is limited to stromal cuffs
surrounding spiral arterioles.

23.  Day 24 - Predecidua bridges multiple vessels and glands in the
functionalis.
 Day 25 - Thin aggregates of predecidua appear below the
endometrial surface which develop into a thick band of by day 26.
 Day 27 - Endometrium shows diffuse predecidual change expanding
downward from the endometrial surface, associated with increasing
numbers of granulocytes.

24. Day 24
Predecidualization
starts in stroma around
spiral arterioles.

25. Predecidualization extends to stroma bridging vessels and
glands of the functionalis. polygonal cytoplasm in
predecidual stromal cells – Day 25

26. Thin layer of predecidua forms in the surface

28.  Earliest feature - Breakdown of the predecidualized stroma,
histologically appears as dense round aggregates of degenerated
stromal cells admixed with inflammation and blood.
 Collapse of the functionalis. Collapsed glands vary in size and shape
and are lined by cells with variable amounts of apical to minimal
cytoplasm(secretory exhaustion)

29. Extensive stromal breakdown in the form of predecidual stromal
aggregates with abundant neutrophils, exhausted secretory glands

30. Arias -Stella reaction : Hypersecretory glands lined by vacuolated
cells with enlarged, hyperchromatic nuclei which protrude into the
lumen - Hobnail.
 Products of conception (in first-trimester samples):
- Immature chorionic villi
- Chorionic plate and membranes
- Intermediate trophoblastic cells admixed with fibrinoid
material at the interface with decidua.

31. Variably sized secretory glands surrounded by a prominently decidualized
stroma, decidual cells have abundant polygonal cytoplasm and ovoid
nuclei with uniform pale chromatin

32. PRODUCTS OF
CONCEPTION
– VILLI.

33. Thin and composed of evenly spaced simple glands lined by
cuboidal to columnar epithelium.
 Round basophilic nuclei with subtle pseudostratification and no
mitotic activity.
Surrounding stroma - dense and uniform.
Atrophic changes : cystic distention of the glands with flattening of
the epithelium – cystic atrophy, epithelial metaplasia and collagen
deposition in the stroma imparting a fibrotic and hypocellular
appearance.
Biopsy and curettage specimens- Inactive endometrial tissue is
often scant and seen as thin strips of surface epithelium with
minimal or absent stroma.

34. Postmenopausal endometrium commonly shows cystic gland dilation
and less cellular areas of stroma with a fibrotic appearance