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Explanation: Again, too late. But for the sake of the glossary, please note that the most common term is "tumor markers". If you want to use Google as your yardstick, it gets 82,000 hits as opposed to 2,200 hits for "tumoral markers" and just 126 for "tumoural markers".
I am very familiar with the term not only because of the translation work I've done but because unfortunately we've had it in the family.