Narrow-Band Imaging Predicts the Histology of Anal Squamous Intraepithelial Lesions and Superficially Invasive Squamous Cell Carcinoma With High Accuracy

Anal cancer is uncommon however its incidence rates have increased in the last decades. Squamous cell carcinoma is the most frequent histologic diagnosis and its development is preceded by precancerous lesions (squamous intraepithelial lesions,SIL). Superficially invasive squamous cell carcinoma (SISCCA) is a microinvasive disease. SIL and SISCCA are amenable to conservative or excisional treatment, however their endoscopic identification is challenging. Narrow-band imaging (NBI) is a “push-of-a-button” technology, which offers the benefits of chromoendoscopy without being time-consuming. Aim of the current study was to evaluate the performance of NBI in predicting histology of SIL and SISCCA. Methods This is a retrospective analysis of a prospectively collected database. All patients with anal lesions suspected for SIL and SISCCA underwent a rectosigmoidoscopy performed using standard high definition colonoscopes (HDTV Olympus 180 Exera) or dual-focus colonoscopes (HDTV Olympus 190 Exera). Three different patterns of NBI were identified: i) pattern I characterized by the elongation of intrapapillary capillary loops (ICL) toward the epithelial surface; ii) pattern II: thickened and tortuous ICL and iii) mosaic-like disposition of the ICL (pattern III). SIL were classified in high-grade (HSIL) and low-grade SIL (LSIL). Correlations between tumor grade (LSIL/HSIL/SISCCA) and NBI was evaluated through the Spearman’s rho coefficient. We calculated sensitivity, specificity, positive and negative predictive values to assess the diagnostic accuracy of NBI (dichotomized as NBI I Vs. NBI II/III) in detecting HSIL or SISCCA (as opposed to LSIL). All tests were two-sided and a p value <0.05 was considered statistically significant. Results From 2009 to 2015, we documented 32 lesions in 29 patients (mean age 54.7 years [SD 12.7]; 16 females [55%]). Most of the lesions (n=23, 72%) were LSIL, while 6 (19%) lesions were classified as HSIL. In three cases (9%), a diagnosis of SISCCA was carried out. NBI pattern was positively correlated to the tumor grade (Spearman’s rho = 0.9385, p<0.001). Furthermore, 23 out of 24 (96%) lesions classified as NBI pattern I were LSIL, all but one HSIL (n=5) presented a NBI pattern II, and all SISCCA (n=3) had a NBI pattern III. The diagnostic accuracy of an NBI pattern II and III in detecting HSIL or SISCCA was high (sensitivity=88.9% [95%CI 51.8–99.7]; specificity=100% [95%CI 63.1–100.0]); the positive and negative predictive values were as high as 100% (95%CI 63.1–100.0) and 95.8% (95%CI 78.9–99.9), respectively. Conclusion NBI evaluation of lesions suspected for SIL or SISCCA can differentiate low from high grade SIL and SISCCA with a very high accuracy. The mosaic-like NBI pattern is strongly associated with the superficially invasive squamous cell carcinoma.