Abstract
Background: Nipple discharge (ND) is one of the most common symptoms encountered by patients with breast disease and can be caused by benign or malignant conditions. ND cytology is a simple non-invasive method to help determine the pathology behind the discharge. This study looks into the diagnostic value and accuracy of ND cytology.
Methods: A retrospective study was performed at a single healthcare center, by evaluating the ND cytology samples and comparing their results with corresponding histopathologic samples from January 2014 to December 2019. Additional data for comparison included ND color, appearance, and discharge laterality.
Results: A total of 499 samples of ND cytology were found, and 98 of these samples had a corresponding histopathologic sample. The overall diagnostic yield was found to be 7.4%, with 462 negative ND cytology samples. The diagnostic yield is highest with bloody discharge (29.8%) and in patients presenting with a unilateral ND (10.8%). Through comparison with corresponding histopathologic samples, the sensitivity of ND cytology in the study is 44.4%, specificity 86.5%, positive predictive value 25%, and negative predictive value 83.9%.
Conclusion: ND cytology is a simple and useful tool for assessing the underlying pathology. Due to the low number of histological samples relating to the cytological samples, larger data would benefit further research. As there are many controversies about ND cytology value, it should be in complement with other investigations to have a better judgment.

Key words: Breast, cancer, cytology, nipple, discharge