PROGRESSION OF CANINE MAMMARY-TUMORS AS REFLECTED BY DNA-PLOIDY IN PRIMARY TUMORS AND THEIR METASTASES

Thirty dogs with metastasizing mammary tumours (carcinomas, n=22; sarc omas, n=8) were necropsied. Flow cytometric DNA analysis was carried o ut on frozen primary tumours and on selected metastases from the dogs. Ductular carcinomas (n=13) had a varying growth pattern, in terms of histology, in both the primary tumours and metastases and between diff erent metastases. The different types of DNA ploidy, including hypodip loidy, in the primary ductular carcinomas were also seen in the tumour metastases. Dogs with primary anaplastic carcinomas (n=7) had multipl e metastases, which were in most cases near-diploid or hyperdiploid. T wo dogs had spindle-cell carcinomas, which were hypodiploid in both th e primary tumour and the metastases. The DNA ploidy in the metastases was retained in 16 of the 22 dogs with primary carcinomas. Fibrosarcom as (n=5) showed different types of DNA ploidy. In two of the three dog s with diploid or near-diploid osteosarcomas, the DNA ploidy was retai ned in the metastases. There was a statistically significant associati on between mammary tumours and metastases (P = 0.0001) in terms of bot h histological diagnosis and DNA ploidy. The association was retained when the carcinomas were tested separately (P = 0.0001); in the sarcom as it was retained weakly in terms of histology (P = 0.0183) but not D NA ploidy (P = 0.6659). The retention of the DNA ploidy in most carcin oma metastases indicated that selection of DNA ploidy had taken place prior to metastasis. The differences in patterns of DNA ploidy between ductular and anaplastic carcinomas may reflect different pathogenesis in these types of canine mammary tumour. (C) 1995 Academic Press Limi ted