  We consider the diphoton production in hadronic collisions at the
next-to-next-to-leading order (NNLO) in perturbative QCD, taking into account
for the first time the full top quark mass dependence. We present the
computation of the two-loop form factors for diphoton production in the quark
annihilation channel, that are relevant for the phenomenological studies of the
full NNLO. The MIs are written in the so-called canonical logarithmic form,
except for the elliptic ones. We perform a study on the Maximal Cut in order to
show the elliptic behaviour of the non-planar topology. The Master Integrals
are evaluated by means of differential equations in a semy-analitical approach
through the generalised power series technique. Finally we use this result with
all the other contributions showing selected numerical distributions.
