Comparative Immunohistochemical Analysis To Distinguish Malignant Mesothelioma (MM) from Reactive Mesothelial Cells (RMC)
Hiroshi Minato, Mana Fukushima, Nozomu Kurose, Takayuki Nojima. Kanazawa Medical University, Uchinada, Ishikawa, Japan
Background: The differentiation of MM from RMC can occasionally present a diagnostic challenge, especially on a small biopsy specimen. Recently several new biomarkers, such as GLUT-1, CD146, and IMP3, have emerged as good candidates for distinguishing MM from RMC. Each study using each marker has reported its high sensitivity and specificity for discrimination between MM from RMC; however, the markers rarely studied by other groups and have not comparatively analyzed. Moreover, CD146 was studied only in cytologic specimens. We, therefore, performed comparative immunohistochemical analysis in MM and RMC cases with antibodies for GLUT-1, CD146, IMP3, EMA and Desmin.
Design: Paraffin-embedded sections from 31 cases of previously confirmed MM and 40 cases of benign lung tissues with RMC were used. 15/31 (48%) MM were epithelioid, 11/31 (36%) were biphasic, and 5/31 (16%) were sarcomatoid. Antibodies used were GLUT-1 (polyclonal, Abcam), CD146 (N1238, Abcam), IMP3 (L523S, Dako), EMA (E29, Dako) and Desmin (D33, Dako). Staining results were scored by percentage of mesothelial or tumor cells staining. When more than 5% of mesothelial/tumor cells were stained with each antibody, the stain was defined as positive.
Results: As positive markers for MM, GLUT-1, CD146, IMP3, and EMA showed sensitivity of 84%, 61%, 94%, and 74%, respectively, and specificity of 100%, 100%, 88%, and 88%. As a negative marker for MM, Desmin showed sensitivity of 48%, and specificity of 97%. In MMs, proportion of positive tumor cells for GLUT-1 was from 10 to 95% (mean 47%); CD146, 6 to 95% (32%); IMP3, 6 to 100% (61%); EMA, 6 to 100 (60%). In RMCs, proportion of positive mesothelial cells for IMP3 was from 10 to 25% (mean 17%); EMA, 10 to 35% (19%); Desmin, 6 to 30% (12%).