Clinical decision-making in atypical and suspicious categories in fine-needle aspiration cytology of the breast.

Background: Fine-needle aspiration cytology (FNAC) is a simple and reliable technique to assess breast lesions, although a definitive differential diagnosis (benignity vs. cancer) is achieved approximately in 60-70% of cases because an inadequate (C1), atypical (C3) or suspicious (C4) category is otherwise reported.

Patients And Methods: A retrospective analysis of 763 cases with C3 or C4 reports was performed to define their positive predictive value (PPV), as well as the practical implications of clinical and imaging findings as for clinical decision-making. FNACs were collected from January 2003 to September 2012 at the Breast Unit of IRCCS "A.O.U. San Martino-IST" Genoa, with each being received later to definitive histology. The PPV for cancer of C3/C4 categories were computed to measure the accuracy of FNAC; moreover, the PPV was also stratified according to clinical, mammography and sonography data alone or by their combination.

Results: The PPV of C3 and C4 was 21.1% (80/380) and 84.1 % (322/383), respectively. Within each C3/C4 category, a significant direct correlation (p<0.001) between the suspicion index of clinical, mammography and sonography data and cancer detection rate was always observed. The PPV of C3/C4 stratified by the combination of clinical and imaging findings showed satisfactory values in the C3 category only when there was an agreement between clinical and imaging findings, whereas the PPV of the C4 category was always remarkably high (ranging from 92.3% to 100%).

Conclusion: the diagnostic work-up in C4 reports or in patients with a C3 report but with an high suspicion index at clinical or imaging examination should be preferably implemented by means of a core biopsy to optimize the therapeutic planning; given a C3 report with dubious clinical and/or imaging findings, an excisional biopsy (or in alternative vacuum-assisted breast biopsy with complete removal of the nodule) should be preferably performed in order to reach a definitive histological dia gnosis with no further delay.