The Japanese Breast Cancer Society Clinical Practice Guideline for pathological diagnosis of breast cancer.

FNAC and CNB are recommended as diagnostic procedures for breast lesions (Grade B). For palpable breast lesions, FNAC has been in use as one of the most reliable diagnostic modalities for many decades. This technique is valuable because of its simplicity, cost-effectiveness, minimal invasiveness and low rate of complications. However, due to limitations of the diagnosis of breast lesions by FNAC, for instance, the difficulty of classifying a breast cancer into noninvasive or invasive carcinoma, its high rates of inadequacy and questionable accuracy, the role of FNAC has been debated recently [1]. In a previous review, the sensitivity of FNAC was reported to range from 65 to 98 % and its specificity from 34 to 100 % [2]. In Japan, a large-scale survey regarding the accuracy of FNAC by the Working Group of the Japanese Society of Clinical Cytology was conducted [3]. The survey showed that the cytological diagnosis had an inadequacy rate of 17.7 %, an indeterminate rate of This article is an English digested edition of the Nyugan Shinryo guideline 2013 nen ban, published by Kanehara & Co., LTD.