BREAST CANCER IN WESTERN AUSTRALIA IN 1989: III. ACCURACY OF FNA CYTOLOGY IN DIAGNOSIS

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Abstract
A population‐based study of all cases of breast cancer diagnosed in Western Australia (WA) in 1989 revealed 701 cases of cancer in 692 women. Three hundred and ninety‐six (56.5%) of these cancers had fine needle aspiration (FNA) cytology. Forty‐three cases were managed non‐surgically, on the basis of an FNA diagnosis and without histologic follow up. Of the cases with histological follow‐up, 73% received an unequivocal diagnosis of malignancy by FNA, and abnormal cells (atypical, suspicious or malignant diagnoses) were reported in 94.2%. Of the cases, 3.2% were reported as benign and in 2.6% the samples taken were unsatisfactory. There were no false positive cytological diagnoses of malignancy. This study is the first to examine the results of FNA diagnosis of breast cancer from a medical community as a whole, rather than for individual or specialist units; the accuracy of diagnosis was similar for different pathology practices including public and private sector laboratories. Lower absolute sensitivity (the proportion of cases given an unequivocal diagnosis of malignancy) was seen in very small and very large tumours, pure duct carcinoma in situ (DCIS), and invasive lobular carcinoma. False negative rates (the proportion of cases given a benign cytological diagnosis) were very low for all laboratories (0–4.5%) and for all types of carcinoma, and the proportion of unsatisfactory samples was exceptionally low for all laboratories (0–4.5%). The overall figures for accuracy are similar to those reported from other centres in Australasia and overseas, and confirm the effective use of FNA cytology throughout the clinical and pathology community in WA.