MOC-31 exhibits superior reactivity compared with Ber-EP4 in invasive lobular and ductal carcinoma of the breast: a tissue microarray study.

Distinguishing between reactive mesothelial proliferations and adenocarcinoma is often very difficult. Ancillary studies, in particular immunohistochemistry, are often critical in detecting malignant epithelial cells, especially in serous effusion specimens. MOC-31 and Ber-EP4 are antibodies which target the epithelial cell adhesion molecule (Ep-CAM, TACSTD1) expressed in epithelial cells, and both are useful in distinguishing metastatic adenocarcinoma from reactive mesothelial cells. However, the reactivity of MOC-31 and Ber-EP4 with breast carcinoma, one of the more common carcinomas involving serous effusions, has not been extensively studied. We analyzed the immunohistochemical expression of MOC-31 and Ber-EP4 using tissue microarrays containing invasive ductal carcinoma (191 cases), invasive lobular carcinoma (44 cases), and 102 other carcinoma types comprising primary carcinomas of lung, gynecologic tract, pancreas, colon, gastric, esophageal, prostate, head and neck, hepatic, and renal origin. For MOC-31, 184 of 191 (96%) invasive ductal carcinomas and 39 of 44 (89%) invasive lobular carcinomas exhibited diffuse positive staining. In contrast, for Ber-EP4, 121 of 183 (66%) invasive ductal carcinomas and 11 of 40 (27.5%) invasive lobular carcinomas exhibited diffuse positive staining. With the exception of 1 case of esophageal adenocarcinoma, all other adenocarcinomas (86 of 87 cases) exhibited diffuse staining with both Ber-EP4 and MOC-31. MOC-31 and Ber-EP4 exhibited identical staining with all other carcinoma types. Our findings indicate that MOC-31 is superior to Ber-EP4 in detecting both invasive lobular and ductal carcinoma of the breast.