Immunohistochemical profile of normal mesothelium and histiocytic/methothelial hyperplasia: a case report

Immunohistochemical profiles of normal mesothelium and histiocytic/mesothelial hyperplasia (HMH) are unknown. A 19-year-old man was treated by thoracoscopic resection of bullae of left lung. Histologically, there were cell proliferative foci composed of round cells without significant atypia (histiocyte, mesothelium and T-lymphocytes). The cell proliferative foci were patch-like, and no invasive features were seen. Because it is composed of histiocytes, mesothelium, and T-lymphocytes, the diagnosis was HMH. Immunohistochemically, cell components of HMH showed the following immunoreactions: calrenitin 3+, D2-40 3+, pancytokeratin AE1/3 3+, pancytokeratin CAM5.2 3+, cytokeratin (CK) 34βE12 1+, CK5/6 1+, CK7 1+, CK8 3+, CK 14 1+, CK18 2+, CK19 2+, p53 10%, Ki67 20%, CD68 3+, CD45 2+, CD45 RO 2+, vimentin 3+, Ber-EP4 -, CK20 -, EMA -, desmin -, CEA -, CA19-9 -, TTF-1 -, S100 protein -, αsmooth muscle actin -, CD34 -, CD20 -, chromogranin -, synaptophysin -, NSE -, CDX2 -, CD56 -, HER2 -, MUC1 -, MUC2 -, MUC5AC -, and MUC6 -. The normal mesothelium showed the following immunoprofile: calrenitin 3+, D2-40 3+, pancytokeratin AE1/3 3+, pancytokeratin CAM5.2 3+, CK34βE12 3+, CK5/6 2+, CK7 2+, CK8 3+, CK 14 -, CK18 3+, CK19 2+, vimentin 1+, p53 -, Ki67 1%, CD68 -, CD45 -, CD45 RO -, Ber-EP4 -, CK20 -, EMA -, desmin -, CEA -, CA19-9 -, TTF-1 -, S100 protein -, α-smooth muscle actin -, CD34 -, chromogranin -, synaptophysin -, NSE -, CDX2 -, CD56 -, HER2 -, MUC1 -, MUC2 -, MUC5AC -, and MUC6 -. These findings indicate that the immunoprolfile of mesothelium in HMH was immunohistochemically very similar to that of normal mesothelium except for CD68, p53 protein, Ki-67 labeling, CD45 and CD45 RO. These indicate that the HMH was reactive phenomenon and HMH is composed of hyperplastic mesothelium, histiocytes and T-lymphocytes. The immunoprofile of normal mesothelium provide basic knowledge of mesothelial pathology.