Factorization of Sums of Polynomials

Let A and B be monic polynomials of the same degree. Given some (or all) information about the individual polynomials A and B, in particular about their factorizations, what can be said about the factorization of their sum C=A+B? We survey results of Fell, Mason and others, and expand upon them. The famous ‘abc conjecture’ of number theory is one obvious motivation for this investigation.