  Using a generalized assumption of Osgood type, we prove a comparison result
between viscosity sub and supersolutions of fully nonlinear, possibly strongly
degenerate, parabolic equations under rather generale assumtpions. The
principle allows to consider dependence on the gradient witha quadratic growth
and also on complex zeroth-order terms. The result it applies in particular to
a differential model for pricing Mortgage-Backed Securities.
