Critical Velocity of Stick-Slip Motion

that women with occult proliferative lesions in the control group pool preferentially refused to volunteer for our study. This seems unlikely. The difference in cytologic results was significant when corrected for age, as indicated in our reference 19. Page and DuPont suggest that we should have removed from the experimental group the two patients with PBD in whom breast cancer was detected during our study. We reported that, in one case, PBD was detected 1 year before the diagnosis of cancer and, in the other, the classification of PBD (on the basis of fine-needle aspirates) was made independent of the suspicion ofcancer (as detected by mammography). Such individuals should be considered as affected with PBD in genetic and statistical analysis. These examples strengthen our contention that cytologic analysis can be an effective diagnostic tool in studies ofgenetic susceptibility to breast cancer. We used a one-tailed test ofsignificance because our hypothesis stated that TBD is more frequent in the clinically normal relatives of two closely related women with breast cancer than in controls.' A two-tailed test, which would be appropriate for detecting positive or negative associations between PBD and breast cancer, also revealed a significant correlation (P < 0.04). We would like to reemphasize that systematic sampling ofthe breast by fine-needle aspiration is strictly a research tool, and we discourage its use as a clinical screening method for asymptomatic women. We have no specific clinical recommendations to make to women who have histologically or cytologically defined PBD (4) other than to follow established screening guidelines. MARK SKOLNICK C. JAY MARSHALL WILLIAM MCWHORTER DAVID GOLDGAR LISA CANNON-ALBRIGHT JOHN H. WAR HARMON EYRE University of Utah Medical Center, Salt Lake City, UT 84132 G. BERRY SCHUMANN University ofAlberta, Edmonton T6G 2R7, Canada D. TIm BISHOP Imperial Cancer Research Fund, Leeds LS2 9LU, United Kingdom