Objective: Evaluation of fine needle aspiration biopsy (FNAB) in the diagnosis of complex cysty of the breast. Materiál and methods: The authors examined 307 complex breast cysty by ultrasonography in 254 patients. Age of patient ranged from 21 to 82. 205 (66 %) of these complex cysty were followed up by ultrasound at 6 - 12 months intervals. Fine needle aspiration biopsy was performed in 102 (34 %) complex cysty. Results: The authors performed FNAB in 102 complex cysty. Cytology of fluid aspirated from 90 cysty was benign. These cysty were followed up by sonography. Cytology showed atypical cells in 7 complex cysty and malignancy in 5 cysty. All these lesions were surgically removed. The postoperative histology of the 7 complex cysty with atypical cytology showed malignancy in one cyst (papillocarcinoma), a benign finding without atypia in one cyst and atypia was conflrmed in the remaining 5 cysty. Malignancy was confirmed by postoperative histology in 4 complex cysty with highly suspected malignancy on FNAB cytology. One patient with a metastasis of NHL in the breast was not operated. Conclusion: FNAB was performed in a group of 102 complex cysty. Malignancy was proved in 6 cysty (5.9 %) and precancerosis in 5 cysty (4.9 %). Authors deduce that FNAB is in certain cases a useful and suitable procedure for the verification of complex breast cysty and it may be a valuable method for further diagnostic or therapeutic steps.

        Key words: complex cysty - FNAB - ultrasound - cytology