Anal intraepithelial lesions

Anal intraepithelial neoplasia, abbreviated AIN, 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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