Enhancing Diagnostic Precision: The Crucial Role of Integrating Cytology, Histology, and Ancillary Testing in Anal Intraepithelial Neoplasia

Summary: Introduction: Anal intraepithelial neoplasia (AIN) poses significant diagnostic challenges due to its diverse histological appearances and considerable interobserver variability. This study underscores the importance of integrating cytological assessments with histopathological correlations and ancillary tests, including P16, Ki-67 immunostaining, and high-risk HPV molecular testing, to enhance diagnostic accuracy and clinical management of AIN. Materials and Methods: In a five-year retrospective study, we retrieved all anal pap smears from our lab information system between 2019 and 2023. A total of 24 cases were collected, revealing a spectrum of cytological and histological findings, ranging from negative for intraepithelial lesion or malignancy (NILM) to high-grade squamous intraepithelial lesions (HSIL). Histologically, the AIN lesions varied from low-grade (AIN 1) to high-grade (AIN 2/3). HPV testing, conducted in 14 cases, identified the viral presence in 10 instances. Results: Discrepancies noted between cytological and histological diagnoses, especially in cases cytologically diagnosed as ASCUS or LSIL, underscored the necessity for further diagnostic refinement. The application of P16 and Ki-67 immunostaining proved pivotal in accurately categorizing high-grade lesions, particularly when cytological interpretations were equivocal. Furthermore, HPV testing provided essential insights into the viral etiology of AIN. Conclusions: The integration of cytological and histological findings with P16, Ki-67 immunostaining, and HPV testing not only refines the diagnostic precision but also facilitates tailored therapeutic approaches. This holistic diagnostic framework significantly contributes to improved patient outcomes by ensuring accurate lesion grading and informed clinical decision-making. Our findings advocate for routine use of this integrated diagnostic approach in the evaluation of AIN to mitigate the inherent limitations of cytology and histopathology alone.