dark finger nails and toenails???

[katsc49]

Hi,
I have stage 4 mestatic breast cancer and been on herceptin and taxotere since January, 2007. Every time my onco sees me he always checks my hands and finger nails, but trecently my nails are all dark and blue and a toe nail, too. It this a side effect, too, of these drugs??
My onco says the lines in my fingernails are there to make them pretty but also said they are cancer lines.
Thank you,
katsc49