Method of immunohistochemistry: what to know

A pathologist places thin sections of tissue on microscope slides and applies selected antibodies. Each antibody is designed to bind to a particular protein. A chemical or dye-based signal makes that binding visible under a microscope. The pattern, strength and location of staining are considered with the tissue’s appearance and the clinical history. A panel of stains is often more informative than a single stain because different patterns can support or weaken possible diagnoses.

The test may help identify the tissue of origin, distinguish tumour types or detect features that affect treatment selection. It is performed on tissue obtained through a Biopsy or another procedure; the report may use terms such as positive, negative, focal or diffuse, which need interpretation in context.

Ask which proteins were tested and what each result means for your diagnosis or treatment. Confirm whether the sample was adequate and whether extra stains, molecular testing or review by a specialist pathologist is needed. Keep the pathology report with your other records. Do not interpret one staining result in isolation: a result can be affected by sample quality, the antibody used and the threshold applied by the laboratory.

Immunohistochemistry itself is a laboratory test, so urgent symptoms usually relate to the biopsy or procedure that supplied the tissue. Seek prompt medical advice for increasing redness, swelling, bleeding, drainage, fever or worsening pain at the biopsy site. Emergency care is appropriate for heavy bleeding, fainting or severe breathing difficulty.

Which stains were performed and why? What diagnosis do the combined findings support? Are any results uncertain? Could the sample need additional testing or specialist review? How will the findings change treatment or the next investigation?