Fine needle aspiration cytology in the work-up of mammographic and ultrasonographic findings in breast cancer screening: an attempt at differentiating in situ and invasive carcinoma.

This study evaluated the results of fine needle aspiration cytology (FNAC) from the first four years of organized mammography screening for breast cancer in Oslo, particularly our policy in differentiating in situ and invasive carcinoma. Lesions were aspirated directly, ultrasound guided, by stereotaxic device or biopsy localization plate. All lesions were aspirated by cytopathologists working with the radiologists at the breast diagnostic centre. Smears were evaluated immediately for assessment of adequacy and a preliminary diagnosis was given to the surgeon. When FNAC revealed malignancy, diagnostic terms were as follows: (1) invasive carcinoma; (2) ductal carcinoma in situ of comedo type (high nuclear grade), cannot evaluate infiltration; (3) ductal carcinoma in situ of low nuclear grade and (4) papillary tumour, cannot evaluate infiltration. There were 953 cases, 70% of which were nonpalpable. Insufficient material was obtained in 5.8%. Absolute and complete sensitivity were 81% and 91%, respectively. Specificity was 85%. There were 448 histologically proven carcinomas. 383 of these were invasive. 362 carcinomas (in situ and invasive) (80.8%) were diagnosed directly on FNAC. Distinction between invasive and in situ carcinoma was possible in 294 of 320 directly diagnosed invasive carcinomas (91.8%). PPV of a diagnosis of invasive carcinoma was 97%. Our data showed that definitive cytological diagnosis of invasive carcinoma was possible in more than 90% of fully diagnostic smears and allowed definitive primary surgery in these women.