Squamous intraepithelial lesion of the uterine cervix

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Squamous intraepithelial lesion of the uterine cervix is a precancerous lesion of the uterine cervix.

It is generally referred to as squamous intraepithelial lesion, abbreviated SIL, though this is somewhat ambiguous as the terminology is being applied to other anatomical sites, e.g. vagina.

In the past, it was known as cervical intraepithelial neoplasia, abbreviated CIN. Prior to that, it was known as cervical dysplasia.

This topic is dealt with from a cytology perspective in the gynecologic cytopathology article.

General

Divided into grades:

  • Low-grade.
  • High-grade.

The new and old terminology

SIL (current terminology) LSIL HSIL
Recent terminology CIN I CIN II, CIN III
Very old terminology mild dysplasia moderate dysplasia, severe dysplasia

Treatment

Overview:

  • LSIL: follow-up, as it usually regress.
  • HSIL: excision (e.g. cone, LEEP, laser) + follow-up.

Procedures

Loop electrosurgical excision procedure (LEEP):

  • Used for squamous lesions -- pathologist typically gets several pieces.

Cone:

  • Used for endocervical lesions, i.e. adenocarcinoma in situ (AIS).
  • Pathologist gets a ring or donut-shaped piece of tissue.

Gross

  • Acetowhite lesion at colposcopy.

Microscopic

Low-grade squamous intraepithelial lesion

High-grade squamous intraepithelial lesion

IHC

Features:[1]

  • p16.
    • Diffuse strong staining involving at least all of the basal aspect of the epithelium = CIN II or CIN III.
    • Patchy, weak positive staining = CIN I or squamous metaplasia.
  • Ki-67.
    • Several positive cells above basal layer suggests CIN II or CIN III.

Notes:

  • Both p16 and Ki-67 are usually negative in CIN I -- 75% of cases.[2]
    • CIN I with p16 staining appears to have a higher risk of progression the p16 negative CIN I.[3]

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ECC - cannot grade

UTERINE CERVIX, BIOPSY:
- FRAGMENTS OF SQUAMOUS EPITHELIUM SHOWING DYSPLASIA, SEE COMMENT.

COMMENT:
The fragments of squamous epithelium do not show full epithelial 
thickness. Thus, while dysplasia is apparent, it is not possible 
to distinguish low-grade from high-grade in this specimen. That said,
there is at least low grade-dysplasia. Follow-up is recommended with 
re-biopsy if clinically indicated.
UTERINE ENDOCERVIX, CURETTAGE:
- FRAGMENTS OF SQUAMOUS EPITHELIUM SHOWING DYSPLASIA, CANNOT GRADE, SEE COMMENT.
- BENIGN STRIPPED ENDOCERVICAL EPITHELIUM AND BENIGN SCANT ENDOCERVICAL MUCOSA.

COMMENT:
The fragments of squamous epithelium do not show the full epithelial thickness; this limits
the interpretation.

A p16 immunostain strongly marks very scant squamous epithelium, and a Ki-67 immunostain
marks increased numbers of squamous cells. 

A cervical biopsy is suggested.

See also

References

  1. Singh, M.; Mockler, D.; Akalin, A.; Burke, S.; Shroyer, A.; Shroyer, KR. (Feb 2012). "Immunocytochemical colocalization of P16(INK4a) and Ki-67 predicts CIN2/3 and AIS/adenocarcinoma.". Cancer Cytopathol 120 (1): 26-34. doi:10.1002/cncy.20188. PMID 22162342.
  2. Jackson, JA.; Kapur, U.; Erşahin, Ç. (Apr 2012). "Utility of p16, Ki-67, and HPV test in diagnosis of cervical intraepithelial neoplasia and atrophy in women older than 50 years with 3- to 7-year follow-up.". Int J Surg Pathol 20 (2): 146-53. doi:10.1177/1066896911427703. PMID 22104735.
  3. del Pino, M.; Garcia, S.; Fusté, V.; Alonso, I.; Fusté, P.; Torné, A.; Ordi, J. (Nov 2009). "Value of p16(INK4a) as a marker of progression/regression in cervical intraepithelial neoplasia grade 1.". Am J Obstet Gynecol 201 (5): 488.e1-7. doi:10.1016/j.ajog.2009.05.046. PMID 19683687.