PAP SMEAR SCREENING

•	Cervical epithelium.
•	Pap smear interpretations. 
•	Follow-up.
•	Treatment.
•	Pap smear screening programme for Singapore.

Cervical epithelium

1.	The cervix is lined by two different types of epithelium:

a.	Ectocervix: covered by squamous epithelium.

b.	Canal of cervix: lined by columnar epithelium.

c.	The point where these two epithelia meet is called the squamo-columnar junction (SCJ).

2.	Squamo-columnar junction:

a.	The position of the SCJ varies throughout reproductive life.

b.	During infancy it lies just at the external os, but as the cervix increases in volume during puberty and also pregnancy the SCJ rolls out onto the ectocervix.

c.	During menopause, it retracts back into the endocervix.

3.	Transformation zone:

a.	That part of the cervix that extends from the widest part of skin that was originally columnar epithelium into the current SCJ.

b.	This area is often characterized by Nabothian follicles. 

c.	Metaplasia occurs here: irreversible physiological transformation of columnar to squamous epithelium. 

Pap smear interpretations

1.	Abnormal cytology:

a.	Dyskaryosis: abnormal nucleus.

b.	Increased nuclear diameter.

c.	Increased nuclear:cytoplasm ratio.

d.	Hyperchromasia.

2.	Degree of dysplasia:

a.	Mild: affects only deepest third of the epithelium from the basal layer upwards with maturation seen more superficial to that.

b.	Moderate: affects two-thirds of the thickness of the epithelium.

c.	Severe: no maturation throughout the full thickness.

3.	Unsatisfactory smear:

a.	A smear that is unreliable for the detection of cervical epithelial cell abnormalities.

b.	A satisfactory smear should show well-preserved and well-visualized squamous cells covering at least one-third of the area of a regular glass slide surface.

c.	If fewer than these are seen because of paucity of cells, poor fixation, air-drying artefact, thick smearing or covering of blood, inflammatory exudates or other contaminants, the smear is considered unsatisfactory.

d.	A smear comprising mainly endocervical cells is also considered unsatisfactory. 

4.	Negative for malignant cells: the smear shows no dyskaryotic or malignant cells, i.e. no cytological evidence of CIN, glandular dysplasia or malignancy.

5.	Atypical squamous cells:

a.	These are cells showing cytologic changes suggestive of a dysplastic squamous lesion that are quantitatively or qualitatively insufficient for a definitive interpretation.

b.	Undetermined significance: cytologic changes suggestive of a low grade squamous lesion but lack criteria for definitive interpretation.

c.	Cannot exclude high grade lesion: cytologic changes suggestive of a high grade squamous lesion but lack criteria for definitive interpretation.

6.	Low grade squamous intraepithelia lesion (LSIL):

a.	HPV effect: squamous cells showing stringent criteria of HPV effect, i.e. koilocytes in superficial or intermediate squamous cells or sharply delineated perinuclear halos in parabasal cells.

b.	Mild dyskaryosis: cytologic changes indicative of CIN 1.

7.	High grade squamous intraepitheliai lesion (HSIL):

a.	Moderate dyskaryosis: cytologic changes indicative of CIN 2.

b.	Severe dyskaryosis: cytologic changes indicative of CIN 3.

c.	Severe dyskaryosis, cannot rule out invasive carcinoma. 

8.	Others:

a.	Squamous cell carcinoma: cytologic changes indicative of an invasive squamous cell carcinoma.

b.	Atypical glandular cells.

c.	Endocervical adenocarcinoma-in-situ.

d.	Adenocarcinoma. 

Follow-up

1.	Negative for malignant cells:

a.	Routine screening schedule.

b.	Squamous cells with inflammatory changes:

i.	treat any infection.

ii.	repeat smear in 4 – 6 months.

iii.	refer for colposcopy if 3rd smear shows similar changes.

c.	Endometrial cells seen: refer to gynaecologist if woman is > 40 years of age.

2.	Unsatisfactory smear:

a.	Treat any infection.

b.	Give a course of estrogen if post-menopausal with atrophic mucosa.

c.	Repeat in 3 months. 

3.	Atypical squamous cells:

a.	Cannot exclude high grade lesion: refer for colposcopy.

b.	Undetermined significance: repeat in 6 months. 

4.	LSIL:

a.	HPV effect:

i.	repeat in 6 months.

ii.	refer for colposcopy if effect remains.

iii.	negative for malignant cells: repeat in 1 year and resume routine screening if normal.

b.	Mild dyskaryosis: colposcopy.

5.	All HSIL lesions are referred for colposcopy. 

Treatment

1.	Natural history:

a.	CIN 1: 

i.	60% regress.

ii.	20% remain.

iii.	< 1% become cancer.

b.	CIN 2 and CIN 3:

i.	60% remain after 10 years.

ii.	10% regress.

iii.	25 – 30% become cancer if left untreated.

2.	Treatment for CIN 2 and 3:

a.	Ablation and excision give 90 – 95% success rate.

b.	Done only if:

i.	whole transformation zone is visible.

ii.	previous histology ruled out invasions.

c.	Complications:

i.	infection.

ii.	bleeding.

iii.	stenosis. 

Screening of cervical cancer

1.	Definition: method of detecting occult disease so that definitive investigation and treatment can be carried out for better survival.

2.	Disease factors:

a.	Common disease in females.

b.	Severe if not treated.

c.	Chronic, slow progressing disease.

d.	Treatment available for early disease: 100% survival.

e.	Early disease can be picked up.

3.	Screening method factors:

a.	Easy to screen.

b.	Cheap.

c.	Acceptable to general population.

d.	Accurate: Pap smear has 85% sensitivity and 80% specificity. 

4.	Target population:

a.	Low risk groups:

i.	virgins.

ii.	females with cervix removed.

b.	At risk: sexually active females.

c.	High risk groups:

i.	promiscuous females.

ii.	prostitutes.

Pap smear screening programme for Singapore

1.	Entry to screening programme: all women who have ever had sex are advised to have their first Pap smear by the age of 25 years.

2.	Frequency of screening:

a.	The second smear is taken one year after the first smear.

b.	Subsequent smears are taken at 3 yearly intervals.

3.	Discharge from screening programme: a woman can be discharged from screening at 65 years of age if the smear taken at 65 years is negative and there was a previous negative smear within the last 3 years.

4.	Women who have never had sexual intercourse:

a.	Women who have never had sexual intercourse need not have Pap smear screening.

b.	However, if these women have any symptoms, they should consult a doctor.