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KRAS mutation status impacts diagnosis and treatment decision in a patient with two colon tumours: a case report
  1. Xiaodong Li1,
  2. G Pezeshkpour1,2,
  3. Ryan T Phan1,2
  1. 1Department of Pathology and Laboratory Medicine, USC/LAC Medical Center, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
  2. 2Department of Pathology and Laboratory Medicine, VA Greater Los Angeles Healthcare System, Los Angeles, California, USA
  1. Correspondence to Professor Ryan T Phan, Department of Pathology and Laboratory Medicine, VA Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Bldg 500, Room 1255, Los Angeles, CA 90073, USA; Ryan.Phan{at}


KRAS mutation status predicts response to anti-EGFR therapy in colorectal cancer patients. Here we report an interesting case of discordant KRAS mutation status in a patient with two separate tumour foci. Tumour A in sigmoid colon invaded through muscularis propria into the subserosal fat with metastatic disease in regional lymph nodes (pT3N2b). Tumour B in ascending colon had a relatively lower stage and no metastasis (pT2N0). Both tumours showed similar morphology, immunohistochemical staining and microsatellite instability pattern. KRAS mutation, however, was detected only in tumour A. These findings indicate distinct clonal nature of these two tumours. The discordance of KRAS mutation status also suggests that a combination of anti-epidermal growth factor receptor and chemotherapy is likely the best treatment option for this patient. This case exemplifies a notion that comprehensive pathological work-up comprising molecular testing is critical to guide the diagnosis and treatment decisions for colorectal cancer patients with multiple tumours.


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