Cytopathology: Gynecologic and Non-Gynecologic
Gynecologic cytology
The Bethesda system governs reporting: specimen adequacy, interpretation, and recommendations. Categories include negative for intraepithelial lesion or malignancy (NILM), organisms, reactive changes, ASC-US, ASC-H, LSIL, HSIL, squamous cell carcinoma, AGC, and adenocarcinoma. HPV testing is integrated as cotesting or primary HPV screening. LSIL usually reflects transient HPV infection; HSIL indicates a precancerous lesion requiring colposcopy. Glandular abnormalities require careful evaluation of the endocervix and endometrium.
Non-gynecologic cytology
Fine-needle aspiration is used for thyroid (Bethesda categories I–VI), salivary gland, lymph node, breast, and pancreatic lesions. Thyroid Bethesda categories guide management: benign, atypia of undetermined significance, follicular neoplasm, suspicious for malignancy, malignant. Fluid cytology distinguishes reactive mesothelial cells from adenocarcinoma using morphology and immunohistochemistry. Urine cytology uses the Paris system, with high-grade urothelial carcinoma as the key target. Sputum and bronchial washings evaluate lung cancer.
Traps
Questions confuse "unsatisfactory" with "negative," or ASC-US with HSIL. Overcalling reactive mesothelial cells as malignant is common. In thyroid FNA, follicular neoplasm is diagnosed by architecture, not by nuclear features.
Rule of thumb: for cervical screening, the threshold for colposcopy is ASC-US with high-risk HPV or worse.
Worked example: a Pap shows koilocytes and mild nuclear enlargement - LSIL; if full-thickness atypia with loss of maturation is present, HSIL. The distinction changes follow-up.