PMS2 immunohistochemistry: what to know

Retained staining means the protein is detected in the tested tumour cells; loss of staining means it is not detected there. Either result needs context, including whether other mismatch repair proteins are retained or lost and whether the internal control stained properly. Loss can be associated with changes in the tumour’s repair pathway, but the stain alone does not establish an inherited condition or determine a diagnosis without the rest of the pathology report.

Ask for the complete pathology interpretation rather than focusing on PMS2 alone. Depending on the pattern and cancer type, the team may recommend review by a specialist pathologist, additional molecular testing, or referral for genetic counselling. The sample usually comes from tissue already collected, although the clinician will explain if more tissue is needed. Keep copies of pathology and genetic results for future oncology appointments.

PMS2 immunohistochemistry itself does not usually cause symptoms because it is performed on tissue in the laboratory. Seek urgent care for symptoms related to your biopsy site, such as heavy bleeding, increasing swelling, severe pain, fever, or difficulty breathing. Contact the clinical team if you do not understand a result before making decisions about treatment or family testing.

Ask whether PMS2 staining was retained or lost, whether the internal controls were satisfactory, and what the other mismatch repair stains showed. Ask if molecular testing or genetic counselling is appropriate, what the result changes about treatment planning, and which relatives may need a separate discussion with a genetics professional.