title: Potential for false-positive staining with a rabbit monoclonal antibody to progesterone receptor (SP2): findings of the UK National External Quality Assessment Scheme for Immunocytochemistry and FISH highlight the need for correct validation of antibodies on introduction to the laboratory.
abstract: This study focused on recent assessment results from the United Kingdom National External Quality Assessment Scheme for Immunocytochemistry and Fluorescence In-Situ Hybridisation breast hormone receptor module in which participants were asked to demonstrate progesterone receptors (PRs). The slides consisted of 3 infiltrating ductal breast carcinomas, previously classified as a high PR expresser, a moderate to low PR expresser, and a negative tumor. During this assessment, 2 commercial rabbit monoclonal antibodies, SP2 (Lab Vision/NeoMarkers, Fremont, CA), and 1E2 (Ventana, Tucson, AZ) were used by 15% of the participants. The SP2 rabbit monoclonal antibody showed false-positive and nonspecific staining on the previously established PR-tumor. This article highlights the necessity for all clinical laboratories to validate immunohistochemical methods and protocols when using newly marketed antibodies such as SP2; use composite tissue blocks with known levels of tumor expression such as a high, mid, and negative expression; and participate in internal and external quality assessment schemes, which can highlight potential technical issues in laboratory methods.
authors.affiliation: Department of Pathology, University College London, London, England.
authors.forename: Merdol
authors.initials: M
authors.lastname: Ibrahim
authors.forename: Andrew
authors.initials: A
authors.lastname: Dodson
authors.forename: Sarah
authors.initials: S
authors.lastname: Barnett
authors.forename: David
authors.initials: D
authors.lastname: Fish
authors.forename: Bharat
authors.initials: B
authors.lastname: Jasani
authors.forename: Keith
authors.initials: K
authors.lastname: Miller
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001943:Breast Neoplasms / Q000378:metabolism; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism; D003429:Cross Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000592:standards*; D007753:Laboratories / Q000592:standards*; D010338:Pathology, Clinical / Q000592:standards*; D011785:Quality Assurance, Health Care; D011817:Rabbits; D011980:Receptors, Progesterone / Q000276:immunology / Q000378:metabolism*; D006113:United Kingdom
chemical_list: D000911:Antibodies, Monoclonal; D011980:Receptors, Progesterone