@mcaplinger
QUOTE
Just because it's spherical now on account of an accident of formation doesn't mean that it meets the definition of a dwarf planet ("has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape")
I think ESO is reaching on this one.
Without attempting to debate the definition of a planet... given some reasonable assumptions about composition, and what is known of Hygia's density and mass, surely this can be quickly settled by calculation, at least to a reasonable approximation?