Significance of atypia in pancreatic and bile duct brushings: follow-up analysis of the categories atypical and suspicious for malignancy.

Brushing cytology is frequently utilized for the investigation of pancreatic and biliary strictures but is associated with low diagnostic sensitivity. The Papanicolaou Society of Cytopathology has presented a system for diagnostic classification which includes the categories benign, atypical, suspicious for malignancy and malignant. We studied a series of 216 pancreatic and biliary brushings with either histologic follow-up or a minimum of 6 months clinical follow-up to determine outcomes for the diagnostic categories ("benign," "atypical, favor reactive," "atypical, not otherwise specified," "atypical, suspicious" and "malignant"). Eighty-six of the 216 (39.8%) were designated "atypical" with 10 of these designated as "atypical favor reactive." Forty-five were called "atypical not otherwise specified" and 31 were interpreted as "atypical suspicious for malignancy." On follow-up, 2 of 10 (20%) "atypical favor reactive" were eventually associated with a malignant diagnosis and 23 of 31 (74.2%) "atypical, suspicious for malignancy" demonstrated a malignant outcome. The remaining 45 brushings in the "atypical" category were "atypical not otherwise specified," and 62% of these were associated with malignancy on follow-up. Stratification of the "atypical" category into "atypical favor reactive," "atypical, not otherwise specified" and "atypical, suspicious for malignancy" improves diagnostic accuracy. The "atypical suspicious for malignancy" category has a follow-up similar to the "malignant" category while the "atypical favor reactive" category is associated with a clinical outcome similar to that of the "benign" category.