Anal intraepithelial lesions

The article deals with anal intraepithelial lesions, abbreviated AILs. They are now classified as either low grade or high grade, as in the uterine cervix.

In the past the term anal intraepithelial neoplasia, abbreviated AIN was used. This is still used frequently.

Regardless of the name, they are considered to be the precursor of anal squamous cell carcinoma.

General

• Precursor lesion of anal squamous cell carcinoma.
• Usually HPV associated.
  • May be prevented by HPV vaccine.

Microscopic

DDx:

• Anal squamous cell carcinoma.

Grading

AIN is graded much like cervical intraepithelial neoplasia:

• High-grade anal intraepithelial neoplasia (HGAIN).
• Low-grade anal intraepithelial neoplasia (LGAIN).

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ANAL CANAL, RIGHT UPPER QUADRANT, BIOPSY:
- LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION (CONDYLOMA ACUMINATUM-LIKE).

ANAL CANAL, LEFT UPPER QUADRANT, BIOPSY:
- LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION.
- RECTAL MUCOSA WITHIN NORMAL LIMITS.

SKIN LESION, PERIANAL, BIOPSY: 
- ANAL INTRAEPITHELIAL NEOPLASIA 3 (SEVERE DYSPLASIA), WARTY-TYPE.
- MARGIN POSITIVE FOR ANAL INTRAEPITHELIAL NEOPLASIA 3.

Micro

There is dysplastic squamous epithelium with coarse chromatin, nuclear hyperchromasia, nuclear enlargement, irregular nuclear membranes, and an increase nuclear-to-cytoplasmic ratio. Mitotic activity is abundant. Several atypical mitoses are identified.

The dysplastic squamous epithelium shows minimal maturation toward the surface (AIN 3). A sizable portion of the lesion show some maturation to the surface (AIN 2).

Inflammation at the dermal-epidermal interface is minimal and the dermal-epidermal interface is well-demarcated. Focal ulceration is present.

The margin of the biopsy has severely dysplastic epithelium (AIN 3).

See also

• Anus.
• LSIL.
• HSIL.

References

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