Dysplasia of the Anus
Definition
- Non-invasive neoplastic changes of anal mucosa
Alternate/Historical names:
- Low grade squamous intraepithelial lesion (LSIL):
- Low grade dysplasia
- Anal intraepithelial neoplasia grade I (AIN I)
- Anal squamous intraepithelial lesion grade I (ASIL I)
- High grade squamous intraepithelial lesion (HSIL):
- AIN II or III
- ASIL II or III
- Bowen disease
- Carcinoma in situ
- High grade or severe dysplasia
- Moderate dysplasia
Covered separately
Diagnostic Criteria
- Superficial, non-invasive lesion of squamous mucosa or skin
- May be flat or occur within a condyloma acuminatum
- Low grade squamous intraepithelial lesion (LSIL)
- Frequently limited to superficial koilocytosis
- Perinuclear clearing
- Hyperchromatic “raisinoid” nuclei
- Irregular nuclear membrane
- May be binucleate
- Orderly maturation
- Low nucleus/cytoplasm ratio < 1:1
- Mitotic figures basal unless inflamed
- No atypical mitotic figures
- Dyskeratosis may be present
- Frequently limited to superficial koilocytosis
- High grade squamous intraepithelial lesion (HSIL)
- Includes both moderate and severe dysplasia, AIN2 and AIN3
- We require the following
- Full thickness atypia
- Disorderly maturation
- Nucleus/cytoplasm ratio ≥ 1:1
- Mitotic figures in upper levels
- Atypical mitotic figures may be present
- Full thickness atypia
- The usual condyloma demonstrates low grade squamous intra-epithelial lesion (LSIL)
- Koilocytes are, by definition, at least LSIL
- High grade squamous intra-epithelial lesion (HSIL) may also be seen
- Invasive carcinoma may be associated with HSIL
- Incidence reported to be 5-25%
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10
