Brown pigmented masses affecting the eye can certainly be a type of cancer called a melanoma. Often these will start on the sclera (white of the eye) and almost bulge into the iris (coloured part of the eye).
Currently treatment of choice is a combination of surgical excision and cryotherapy (freezing the stump!) to try and prevent recurrence.
Due to the technical difficulty of this type of surgery, it has to be performed by an ophthalmic specialist, with a special operating microscope. This is highly skilled surgery and can be expensive.
In some cases, if surgical treatment is not possible, then it may be necessary to remove the whole eye. This is usually more drastic for the owner than the pet! Once over the surgery, all pets recover and can lead a perfectly normal life.
My advice - take up the refferal option, get it checked by the specialist, and then you will know exactly where you stand.
Good luck