Tissue Microarrays Are an Effective Quality Assurance Tool for Diagnostic Immunohistochemistry

• Published in: Modern pathology 2002-12, Vol.15 (12), p.1374-1380
• Main Authors: Hsu, Forrest D, Nielsen, Torsten O, Alkushi, Abdulmohsen, Dupuis, Bev, Huntsman, David, Liu, Chih Long, van de Rijn, Matt, Gilks, C Blake
• Format: Article
• Language: English
• Subjects: Biomarkers, Tumor - analysis; Cluster Analysis; Diagnosis, Differential; Female; Histocytological Preparation Techniques - methods; Histocytological Preparation Techniques - standards; Humans; Immunohistochemistry - methods; Immunohistochemistry - standards; Keratins - analysis; Laboratory Medicine; Male; Medicine; Medicine & Public Health; methods-in-pathology; Neoplasms - metabolism; Neoplasms - pathology; Pathology; Quality Control; Reproducibility of Results; S100 Proteins - analysis
• ISSN: 0893-3952; 1530-0285
• DOI: 10.1097/01.MP.0000039571.02827.CE

There has been considerable variability in the reported results of immunohistochemical staining for some diagnostically relevant antigens. Our objectives in this study were to (1) use a multitumor tissue microarray with tissue from 351 cases received in our department, representing 16 normal tissues and 47 different tumor types, to compare immunohistochemical staining results in our laboratory with published data, using a panel of 22 antibodies; (2) assess interlaboratory variability of immunohistochemical staining for S-100 using this microarray; and (3) test the ability of hierarchical clustering analysis to group tumors by primary site, based on their immunostaining profile. Tissue microarrays consisting of duplicate 0.6-mm cores from blocks identified in the hospital archives were constructed and stained according to our usual protocols. Antibodies directed against the following antigens were used: B72.3, bcl-2, carcinoembryonic antigen, c-kit, pankeratin, CD 68, CD 99, CK 5/6, CK 7, CK 8/18, CK19, CK 20, CK 22, epithelial membrane antigen, estrogen receptor, melan-A, p53, placental alkaline phosphatase, S-100, synaptophysin, thyroid transcription factor-1, and vimentin. Staining results on the array cases were compared with published results, and hierarchical clustering analysis was performed based on the immunohistochemical staining results. Unstained slides of the multitumor tissue microarray were sent to five other diagnostic immunohistochemistry laboratories and stained for S-100 protein. The staining results from the different laboratories were compared. Staining results using our current methods and samples from our laboratory were compatible with those described in the literature for most antigens. Placental alkaline phosphatase staining was not specific with our protocol, showing staining of a broad spectrum of different tumors; this finding initiated a review of our recent requests for placental alkaline phosphatase immunostaining and revealed two instances in which placental alkaline phosphatase positivity was incorrectly interpreted as evidence of a germ cell tumor. S-100 staining was less sensitive but more specific for the diagnosis of melanoma or neural tumor in our laboratory, compared to some published reports. Assessment of interlaboratory variability of S-100 immunostaining showed that there was more frequent staining of carcinomas in some laboratories, resulting in decreased specificity of S-100 staining in distinguishing melanoma f