Can breast cancer be spotted through a chest ct scan?

Yes: Yes though that is not the test of choice. A chest ct will usually spot breast cancer as an incidental finding. It is not as sensitive as a mammogram or ultrasound of the breast.

Sometimes: But the lesion would have to be large enough to be visualized. A mammogram is a much superior means to evaluate the breast.

Yes and no: A mammogram and ultrasound ate the best way to diagnose a breast mass. However a ct scan may show a obvious large mass or asymmetry in the breast tissue which may lead to a mammogram. A ct scan also may show enlarged lymph nodes which may be a clue.