In this paper, we study the singular vortex patches in the
two-dimensional incompressible Navier-Stokes equations. We show,
in particular, that if the initial vortex patch is $C^{1+s}$
outside a singular set $\Sigma$, so the velocity is, for
all time, lipschitzian outside the image of $\Sigma$ through the
viscous flow. In addition, the correponding lipschitzian norm is
independant of the viscosity. This allows us to prove some results
related to the inviscid limit for the geometric structures of the
vortex patch.