[Needle aspiration cytology of the breast: current perspective on the role in diagnosis and management]

Abstract

The aim of this review is to highlight the continuing role of fine needle aspiration cytology (FNAC) in the diagnosis of breast lesions, against a background of its diminishing use in some centres, particularly those involved in breast screening, because of its controversial inadequate rate and suboptimal accuracy. This review explores the current practice and confirms the continuing role of FNAC in the diagnosis and management of breast lesions. The three main areas where FNAC still plays a major role are the following: (a) diagnosis of benign disease in symptomatic palpable lumps as part of triple assessment; (b) staging of breast carcinoma, in particular preoperative axillary lymph node FNAC and intraoperative sentinel node imprints; and (c) diagnosis of metastatic disease at distant sites following treatment for carcinoma. Excision biopsy of the lesion to establish whether it is benign or malignant is not an acceptable mode of diagnosis any more. When triple assessment is concordant, final treatment may be ensued without open biopsy. Triple assessment is a cost effective, easy to perform and time saving approach, however, it can only be used at those institutions where excellent imaging facilities as well as services of a cytopathologist are available. The majority of European countries use similar reporting system for breast FNAC (C1-C5), in keeping with European guidelines for quality assurance in breast cancer screening and diagnosis. A clear reporting system ensures that an unequivocal cytological diagnosis of malignancy is reliable, and in cases where mammography/ultrasonography and clinical examination are in agreement with FNAC, frozen section examination is unnecessary. Suggested thresholds for cytology performance (where therapy is partially based on FNAC) according to the UK NHSBSP are the following: absolute sensitivity (C5 only) >70%, complete sensitivity (C3, C4, C5) >90%, specificity >65%, positive predictive value >99%, false negative <4%, false positive <0.5%, inadequate rate <15%, inadequate rate from cancers <5% and suspicious rate <15%. The issue of optimal sampling to obtain adequate cell material in sufficient quantity is of paramount importance when assessing the accuracy of FNAC. The inadequate rates in FNAC from different sources are lowest when FNAC is performed by a cytopathologist and highest when done by a non-cytopathologist. The multidisciplinary approach is necessary to amplify FNAC quality and to reduce its diagnostic limits. Only when this model of activity is not available, the role of FNAC is less effective and the addition of core biopsy (CB) to FNAC should be considered. CB as an alternative diagnostic modality should be used advisedly, in situations where it is more likely to yield diagnostic information, e.g., in the diagnosis of impalpable masses, microcalcifications or a clinically apparent malignancy where preoperative chemotherapy is planned. CB should not be used as a substitute for poor performance at FNAC. The methods are not mutually exclusive. Where there is access to skilled cytopathologists, FNAC and CB can complement each other and provide a highly accurate, rapid and cost-effective means of patient triage. FNAC has an advantage of being an immediate and excellent method for on-site examination and one-stop diagnosis at breast outpatient clinics. Since the majority of patients attending a breast clinic have benign disease, they benefit from rapid diagnosis and discharge from the clinic. Sentinel node biopsy, now used routinely during the operation for breast carcinoma with the aim of achieving "one-step" surgery can be reduced by one third of patients who ultimately require axillary node dissection if preoperative image guided FNAC of the axilla is used. Positive intraoperative imprint cytology is a reliable tool for proceeding to axillary node dissection, the method having a very high specificity in all published series. FNAC remains the method of choice of diagnosing metastatic disease at extramammary sites. Hormone receptor status, but not HER 2, can be reliably assessed from cytological material. Cells carry a promise of molecular diagnosis and targeted treatment in the future. The future of breast FNAC is bright.