Gynecologic and Anal Cytopathology
Key Concepts
- Bethesda System for Cervical Cytology: Understand categories (NILM, ASC-US, LSIL, ASC-H, HSIL, AGC, AIS, carcinoma) and their management implications.
- HPV Biology: Link HPV types (16, 18, 31, 33, etc.) to lesion severity; recognize HPV cytopathic effect (koilocytosis).
- Anal Cytology: Apply similar Bethesda terminology; know risk groups (HIV+, MSM) and sampling techniques.
- Glandular Lesions: Differentiate AGC subtypes (endocervical, endometrial, extrauterine) and AIS from invasive adenocarcinoma.
- Organisms and Contaminants: Identify Candida, Trichomonas, bacterial vaginosis (clue cells), HSV, and Actinomyces.
Common Traps
- Overcalling ASC-US vs. LSIL: A single koilocyte is insufficient for LSIL; require clear HPV cytopathic effect.
- Underestimating ASC-H: High-risk HPV positivity in ASC-H warrants colposcopy; do not dismiss as reactive.
- Misclassifying AGC: AGC favors glandular neoplasia; endometrial cells in postmenopausal women require workup.
- Anal Cytology Pitfalls: Hyperkeratosis and radiation changes can mimic dysplasia; use HPV testing as adjunct.
- Contamination: Lubricant or talc can mimic koilocytes or clue cells; correlate with clinical history.
Rule of Thumb
For ASC-US in women ≥25, reflex HPV testing is preferred; if HPV positive, colposcopy; if negative, repeat cotest in 3 years. For ASC-H, colposcopy regardless of HPV status.
Worked Example
A 30-year-old woman has ASC-US on Pap. Reflex HPV is negative. Management: repeat cotest in 3 years (per ASCCP 2019 guidelines). If HPV positive, colposcopy.