  We derive the exact Casimir-Polder potential for a polarizable microparticle
inside an ideal metal cylindrical shell using the Green function method. The
exact Casimir-Polder potential for a particle outside a shell, obtained
recently by using the Hamiltonian approach, is rederived and confirmed. The
exact quantum field theoretical result is compared with that obtained using the
proximity force approximation and a very good agreement is demonstrated at
separations below 0.1$R$, where $R$ is the radius of the cylinder. The
developed methods are applicable in the theory of topological defects.
