What should you know about KRAS immunohistochemistry?

A laboratory prepares thin sections from a biopsy or operation specimen and applies an antibody designed to bind a target. A visible colour or signal can show whether the target is present in the tested cells. The pathologist interprets the signal with the tissue pattern and appropriate controls.

KRAS is a protein involved in cell-growth signalling. Immunohistochemistry may support a pathology assessment, but it differs from molecular testing, which examines the tumour's genetic material for a specific mutation. A result may be positive, negative, weak, or difficult to interpret, and the meaning depends on the antibody and laboratory method used.

Ask whether the report describes protein staining, a specific KRAS mutation, or both. Confirm which tissue was tested, whether there was enough tumour in the sample, and whether an additional molecular test is recommended. Results are considered alongside tumour type, location, stage, other biomarkers, and general health.

Do not use a KRAS stain by itself to choose or stop treatment. Your oncology team can explain whether the finding changes eligibility for a targeted approach, chemotherapy, an immunotherapy discussion, or another plan. A repeat biopsy is not always needed, but the team can explain its purpose if the sample is limited or the result is unclear.

The laboratory test itself does not usually create new symptoms. Contact the clinical team about worsening breathlessness, chest pain, coughing blood, severe weakness, confusion, or a rapidly changing symptom while diagnostic or treatment planning is underway.

Seek emergency help for severe difficulty breathing, fainting, blue lips, heavy bleeding, or sudden neurological changes. Bring the pathology report and current medicines when attending urgent care if it is safe to do so.

Ask: Is this an immunostain or a molecular KRAS test? Which antibody or mutation was assessed? Was the sample adequate? Do I need broader genomic testing? How does the result affect the treatment choices being discussed?