App note from ROHM Semiconductor on the importance of sense trace/line arrangement on PCB designs. Link here (PDF)
While resistance, power rating and size are important considerations when using shunt resistors, tolerances that affect the accuracy of the detected voltage must also be considered. These tolerances include the temperature coefficient of resistance and the tolerance of resistance at room temperature.
The temperature coefficient of resistance indicates the change in resistance value due to a change in temperature of the resistor. Since resistance is affected by component temperature rise as current flows through and power is consumed, and ambient temperature changes, the temperature coefficient of resistance is an important factor in accurately detecting current values.