Near tetraploid prostate carcinoma: Methodologic and prognostic aspects

Abstract

The clinical value of DNA ploidy analysis in prostate carcinoma has been an issue for investigation for more than 2 decades. In general, diploid or pseudodiploid tumors are associated with a favorable prognosis and aneuploid tumors with an unfavorable prognosis, irrespective of type of treatment. Tumors with DNA values in the tetraploid region (around 4c) present a diagnostic problem. Such DNA distributions may clearly represent aneuploid tumors with an unfavorable prognosis. However, a 4c distribution may conversely represent a tetraploid tumor (possibly a polyploid variant of the diploid tumor) with a favorable prognosis. Previous data from our laboratory indicate the existence of such a tetraploid subgroup. The goal of the current study was to investigate the diagnostic problem of 4c tumors in greater detail. Ploidy classification of cytologic smears by image cytometry was performed in a retrospective study of 334 patients with hormonally treated prostate carcinoma. Follow-up time was 30 years or until death. Three ploidy types were defined: near-diploid (D type), near-tetraploid (T type), and highly aneuploid (A type). Tumors with a modal value within the tetraploid region were found in 27% (92 cases) of the total material. Of these, 9% were defined as T type and 18% as A type. Overall, 37% of the tumors were classified as D type, 9% as T type, and 54% as A type. Of the A type tumors, one-third had modal DNA values in the tetraploid (4c) region. Multivariate analysis showed a statistically significant difference between A type tumors and D and T type, but not between D type and T type. Both D and T type tumors progressed slowly and killed the patients 5 to 30 years after diagnosis, whereas A type tumors progressed rapidly and killed the patients within 6 years of diagnosis. By image cytometry, prostate carcinoma can be divided into three ploidy types: D, T, and A type. Biologically, however, the tumors fall into only two groups: low grade malignant, pseudodiploid tumors of D or T type, and high grade malignant, highly aneuploid tumors of A type.