We consider optimal control problems governed by semilinear par-
abolic equations with nonlinear boundary conditions and pointwise constraints
on the state variable. In Robin boundary conditions considered here, the nonlinear term is neither necessarily monotone nor Lipschitz with respect to the
state variable. We derive optimality conditions by means of a Lagrange multiplier theorem in Banach spaces. The adjoint state must satisfy a parabolic
equation with Radon measures in Robin boundary conditions, in the terminal
condition and in the distributed term. We give a precise meaning to the adjoint equation with measures as data and we prove the existence of a unique
weak solution for this equation in an appropriate space.