Tumor uptake in MDA-MB-468 xenograft models was 15 ± 3.1% ID/g with T/B ratio of 12 ± 1.4 at 24 h p. i., indicating that 99mTc-PmFab-His6 is a promising probe for imaging EGFR and may be used to monitor the response to EGFR-directed therapies. The gene discussed is EGFR; the disease is neoplasm.