It has been suggested that prostate cancer spread has predictable patterns, with prostate cancers known to affect the prostatic contours. However, few systematic investigations have documented the associated contour alterations, especially at a clinically localized stage. The purpose of the present paper was to objectively evaluate prostatic contour alterations based on left-right asymmetry, and analyze the histopathological features and prognostic impact. One hundred and sixty-two asymmetrical contours with left-right asymmetry in the length >or=10%, and 278 cancer foci were observed in 114 radical prostatectomy specimens. Of the asymmetrical contours, 55 (34%) were caused by cancer, and of the cancer foci, 55 (20%) generated asymmetrical contours. Cancer-associated asymmetries showed significant correlations with aggressive behaviors such as cancer volume, Gleason score, positive surgical margin, and extraprostatic extension, although these were not significantly associated with unfavorable prognosis. The authors present basic data relating to altered prostatic contours, such as spatial distribution and causative pathological conditions. Clinicopathological characteristics concerning cancer-associated contour alterations, are also presented in detail.