The true nature of atypical breast cytology

Breast cancer is the most prevalent cancer in women in the western world including Australia. Early detection and accurate diagnosis of new breast lesions is essential for appropriate medical management. Fine needle aspiration (FNA) is a cytological investigative tool commonly used to provide the initial pathological diagnosis of breast lesions. An atypical cytology report (C3) is an ambiguous or equivocal result. This uncertainty creates a dilemma and a more invasive investigative procedure such as core biopsy or incisional biopsy may be required, which comes at greater cost and anxiety to the patient. The aims of this project were to understand the true nature of C3, to determine the underlying causes of C3 and to devise a strategic approach to minimise its use without compromising the other cytological categories. The practical aims were to create a greater understanding of the issue and to produce a collective uniform approach to reporting atypical breast cytology cases thereby refining its use. The results of a blind rescreen of 256 consecutive C3 cases were statistically analysed. From these results, a cytomorphological approach to assess the risk of malignancy was developed and tested against a validation set of 230 subsequent C3 cases. Various strategies have been developed to reduce the incidence of the C3 category. Extrinsic factors can be easily reduced by greater involvement by cytology staff in the FNA procedure. Intrinsic factors can be understood and considered when allocating cases into C3. Specific diagnoses, such as papillary neoplasm can direct more appropriate definitive management. The cytologists in our institution have gained greater awareness of the atypical category by actively participating in the project and by having access to teaching resources and examples. The benefits manifest as financial, medical and social enhancements. It is hoped that some of these approaches will be taken up by other institutions in Australia and internationally.