Growth and histology of four canine mammary tumour lines established in nude mice.

A colony of nude (BALB/c/Nu/Nu) mice has been established and used to produce and study transplantable tumour lines derived from spontaneously occurring canine mammary neoplasms. Four primary tumours of differing morphological types were studied. Two were adenocarcinomas (MS306 and PD6014) with varying degrees of differentiation, the third (F5010) was a complex adenocarcinoma composed of both stromal and epithelial elements and the fourth (V5500) was a fibrosarcoma. Tumour fragments were implanted into the subcutaneous tissue of 4- to 6-week-old mice and resulted in tumour growth in each case. There was a latent period of 1 month for tumours PD6014, F5010 and V5500 and of 3 months for tumour MS306 before tumour growth ensured. After serial transplantation this period decreased to 1-2 weeks for the first 3 tumours and to 6 weeks for the last. After the initial lag period, tumour volume increased logarithmically in all cases with doubling times of 6-20 days. Each tumour line has been passaged through 3 serial transplantations with 3 of the tumours retaining their original histological appearance whilst the fourth became slightly more dedifferentiated.