There is no definitive definition in reporting system in Europe. To maximize the mutual understanding and to improve the diagnostic standardization all  breast FNA’s cytology specimens should be coded using one of the following five reporting categories as defined by the U.K. Breast Screening Programme in 1993 in the U.K. These categories are:

C1: Inadequate
C2: Benign
C3: Atypia probably benign
C4: Suspicious of malignancy
C5: Malignant