Ploidy and DNA distribution analysis of spontaneous dog tumors by flow cytometry

Ploidy and DNA content distributions were measured for 68 biopsy specimens of spontaneous (solid) dog tumors using flow cytometry analysis of mithramycin-stained cells. The tumor ploidy (i.e., DNA index values) ranged from 1.0 to 4.0 (diploid = 1.0), with a mean of 1.4. More than 80% of the tumors had elevated G0-G1 peak DNA contents and were classified heteroploid, similar to human solid tumors. Six mammary carcinomas and osteosarcomas had bimodal G0-G1 peaks. Based on flow cytometric data and pathology criteria, it was observed that: (a) the percentage of tumor S-phase cells tended to increase with increasing DNA index; and (b) for a given DNA index, the percentage of S-phase cells was lower for well-differentiated tumors and higher for poorly differentiated tumors. The inherent scattering of the DNA content and DNA distribution data between different tumor types limited the usefulness of these data for classifying tumors. The results suggest that improved classification of cytologically different tumors and tumor subsets might be achieved by simultaneous flow measurement of DNA content and DNA distribution information with an additional parameter that detects the cytological differentiation state.