Evidence-based guidelines for the utilization of immunostains in diagnostic pathology: pulmonary adenocarcinoma versus mesothelioma.

There are no firmly established guidelines for the use of antibodies in immunohistology as individual tests or panels. Practicing pathologists must rely on information available in individual publications, review articles, books, and internet-based databases to develop diagnostic immunohistochemical algorithms for their individual practices. In contrast, other medical specialties have crafted many evidence-based practice guidelines (EBG) that are widely used; these have helped to augment standardization and cost effectiveness. In particular, the use of several "epithelial" and "mesothelial" antibodies has been proposed to distinguish epithelioid malignant mesothelioma from metastatic pulmonary adenocarcinoma. Other authors have previously done systematic literature reviews of this subject up through 2004 and integrated the results of 88 publications into summarized test-performance values for 15 preselected immunohistochemical markers. The results suggested that 7 tests provide optimal sensitivity and specificity (MOC-31, BG8, CEA, TTF-1, CK5/6, WT-1, and HBME-1), but they provide no guidance for integration of such data into EBG. Odds ratios (ORs) were employed to compare the effectiveness of any single test, and chosen combinations thereof, in the differential diagnosis of malignant mesothelioma and metastatic pulmonary adenocarcinoma. Surprisingly, selected single immunostains or antibody pairs yielded ORs (varying from 96.34 to 1233.19) that were equal or better in efficacy when compared with more comprehensive panels. These results support the potential value of systematic reviews, meta-analysis, and OR calculations for development of EBG in diagnostic immunohistology.