liver metastesis

My mother had kidney cancer about 5 years ago. They removed the kidney and she has been clear since. In Jan of this year, she just all of a sudden swelled up...her face, her legs, her arms and started getting "bruising" spots all over her body. They figured out soon enough that her pituitary gland had stopped working and started on giving her hormones to compensate. They did a full body scan and said "no cancer". In April, her liver enzymes and PT,PTT  went up a bit ...did a liver biopsy, was pronounced normal. Then they said that maybe her liver was out of wack because of her large does of cholesterol meds, so they took her off those for a while to see if the enzymes corrected. They didn't. So they did other liver testing, and said while the tests were not normal, they were not "too bad". THEN after a CT scan of her chest, they said they saw "some spots" on her liver and were suspicious of liver metastisis. Can it happen that fast or could they have missed it, even with all of her extensive testing? Wouldn't liver metastisis occured to them sooner..since it would be a seconardy cancer?