Retrospective Rescreening of Negative Cervical Cytology Samples Preceding Histologically Proven CIN2-3 and Squamous Cell Carcinoma: An Educational Opportunity to Understand and Prevent Laboratory Errors

OBJECTIVES

We aimed to analyze the false-negative (FN) liquid-based cytology diagnoses from the 5 years preceding all the 2013 histologically proven cervical intraepithelial neoplasia (CIN)2-3 and squamous cell carcinoma (SCC) and to propose corrective actions.

STUDY DESIGN

This was a retrospective, blinded rescreening ('5-year look-back') of liquid-based cytology samples with negative categorizations, which occurred before histologically proven CIN2-3 and SCC.

RESULTS

The FN rate was 7.8% (21/256 samples preceding CIN2-3 and 0/13 samples preceding SCC). Slides confirmed as 'negative', 'interpretation error' and 'screening error', respectively, were 3.3% (9/269), 2.6% (7/269) and 1.9% (5/269). In 9/12 cases, error was associated with small atypical cells. In 7/12 cases, these diagnostic cells were less than 5/10 HPF. Inflammation and prominent reactive changes were present in 5/12 cases. Five patients had a positive clinical history. In 2 cases, there were multiple-cell-layer artifacts. Dense groups of small blue atypical cells were missed in 2 other cases. Dotting was imprecise in 6/7 samples.

CONCLUSION

Considering the above results, we specifically reoriented our continuous education activities, focusing rapid rescreening on scanty, isolated, small, atypical cells and dense cell groups. Prior to final diagnosis, pathologists should systematically review the entire surface of the dotted slides, with special attention being devoted to slides with multiple cell layers and tridimensional groups.