Horseradish peroxidase immunohistochemistry

A laboratory prepares thin sections from a biopsy and applies an antibody designed to bind a particular protein. The antibody is linked to horseradish peroxidase, an enzyme. When the laboratory adds a suitable chemical, the enzyme creates a coloured signal where the antibody has attached.

A pathologist examines the stained tissue with a microscope and interprets the pattern, location and strength of staining alongside the tissue's appearance. The stain is one part of a pathology assessment; it is not a diagnosis by itself.

Ask which marker was tested, whether the result was positive, negative, weak or strong, and how the finding fits the biopsy diagnosis. Some results guide tumour classification or treatment selection, while others help distinguish tissues that look alike.

Keep the full pathology report and ask whether additional stains, molecular tests or review by a specialist pathologist are needed. The meaning depends on the marker, tumour type, sample quality and the laboratory's interpretation.

The stain itself is performed on tissue in the laboratory and does not usually create a new symptom. Contact the clinician who arranged the biopsy for increasing pain, bleeding, redness, swelling or fever at the biopsy site, and seek urgent help for heavy bleeding or severe illness.

Which protein was stained? What does the staining pattern mean for my diagnosis? Is the result enough to guide treatment? Could another test clarify it? When will the complete pathology interpretation be available?