Mammographically-guided fine needle aspiration in differential diagnosis of cystic versus solid rounded masses smaller than 2 cm detected at mammographic screening.

Purpose: To evaluate mammographically-guided fine needle aspiration (FNA) in the differential diagnosis of smaller cystic and solid rounded masses, detected at screening.

Materials And Methods: All mammographically-guided FNAs performed in a consecutive series of 5013 women recalled in a population-based screening programme were reviewed. FNA was done with a perforated compression plate in 369 masses and stereotactically in 259 masses. More than 3 years of mammographic follow-up were available for 267 cysts. Results from ultrasound examinations were available for a subset of 69 cysts.

Results: A total of 344 rounded masses were diagnosed as benign cysts and 284 as solid masses. Surgical biopsy was performed in 75 masses. Two surgically biopsied masses proved to be cysts, one where the aspirate was misinterpreted as suspicious for mucinous cancer, and one where FNA failed to prove a cyst. In another case initially regarded as cyst, a rounded ductal cancer in situ was diagnosed 2 years later in the same location. Thus, among 267 masses diagnosed as benign cysts and followed up for 3 years, only one proved to be malignant. Ultrasound failed to visualise 35% (24/69) of smaller cysts.

Conclusion: Mammographically-guided FNA is a valuable method to differentiate smaller cysts from solid rounded masses and hence to avoid unnecessary surgical biopsies.