A pump assembly (1) includes an impeller (12) with a rotor axis (R), a pump housing (11) accommodating the impeller (12), a drive motor with a stator (14) and a rotor (51) for driving the impeller (12). A rotor can (57) accommodates the rotor (51), and a stator housing (13) accommodates the stator (14). The rotor can (57) includes a rotor can flange (63) having a lateral rotor can flange face (87) fitting within a peripheral wall (69) of the pump housing (11). The lateral rotor can flange face (87) has at least three radial projections (91) abutting against the peripheral wall (69) of the pump housing (11) and centering the rotor can (57) with respect to the peripheral wall (69) of the pump housing (11).