NUMERICAL CHROMOSOMAL-ABERRATIONS IN TRANSITION-ZONE CARCINOMAS OF THE PROSTATE

Purpose: Prostatic carcinomas arising in the transition zone (TZ) are thought to differ from the more frequent cancers of the peripheral zon e (PZ) with regard to morphology and biologic behavior. It is unclear, however, whether the differences are reflected in genetic alterations . Materials and Methods: We assessed numerical aberrations of chromoso mes 7, 8, 10, 17, and X with interphase cytogenetics in 10 radical-pro statectomy specimens containing exclusively TZ cancers larger than 0.5 cm.(3) and in 10 additional specimens containing bath TZ and PZ cance rs larger than 0.5 cm.(3) each. Results: Of the 20 TZ carcinomas, 9 we re completely disomic, 5 were at least focally tetrasomic but not aneu somic, and 6 were focally aneusomic. Ploidy correlated well with tumor volume (p = 0.0083), grade (p = 0.0064) and surgical margins (p = 0.0 141) but not with preoperative prostate-specific antigen. A strong cor relation was observed between the presence of low grade tumor (Gleason grade 4 or 5) and a nondiploid chromosomal status (p = 0.0001). In 10 cases there were also foci of PZ cancer larger than 0.5 cm.(3), of wh ich 4 were disomic, 3 were tetrasomic at the most, and 3 were aneusomi c. The mean tumor volumes of disomic and aneusomic cancers differed si gnificantly between TZ and PZ carcinomas (p = 0.0336 and 0.0476, respe ctively). Conclusions: Numerical chromosomal instability parallels tum or progression in TZ carcinomas of the prostate. However, our results indicate that PZ and TZ cancers differ in that the latter can reach la rger volumes before histological dedifferentiation and aneusomy occur.