GPNMB and neoplasm: GPNMB reactivity is non‐specific and cannot distinguish between FLCN‐mutated tumours and TFE3/TFEB RCCs, as well as various other TSC1/2/MTOR‐mutated tumours, but it may be diagnostically useful for screening for FLCN mutations that would help distinguish them from their mimics.53, 59