I'm not sure whether you are uncertain whether you want a second opinion about the diagnosis or your treatment options.  I think a second opinion is never a waste of time because a different doctor can either reassure a patient she is on the right treatment track or offer some additional options.  Assuming the biopsy was read in a reputable lab, I doubt they made a mistake about the basic diagnosis of cancer.  I don't know why your discharge stopped after the biopsy, but a discharge that lasted for years may not be related to cancer at all.  Usually over the course of years, you would have seen the growth of a lump or development of other cancer symptoms besides the discharge.

Another doctor might be able to give you some additional insight into the relationship between the discharge and the cancer they found, so it wouldn't hurt to see someone else.  A good place to go for a second opinion is a comprehesive cancer center.