A mouse model of breast cancer metastasis to the choroid of the eye.

Transformed mouse mammary epithelial cells, r3T, injected into the arterial circulation form bone metastases with high frequency. Here we report that metastases to the choroid of the eye also occur in these mice with a penetrance of at least 50%. The tumors can occupy as much as half the volume of the eye, and pigmented cells become incorporated into and distributed throughout the tumors. Pigmentation is also observed in the brains and optic nerves of mice with choroidal tumors, suggesting that the tumor cells stimulate migration of pigmented cells along the optic nerve into the brain. To our knowledge, this is the first mouse model of breast cancer choroidal metastasis, and should be useful in the study of this disease.