Floating ground plane and static
The body of the PT100 is normally not in contact with the 2,3 or 4 wires from the PT100. You can therefore connect the body to ground without any problem and connect the resistor to the input of your system

Frequently the housing is connected to a shielded cable. The wires from the resistor are floating. For proper use the shielding should be connected to ground and the wires to the system.