CD44H EXPRESSION IN REACTIVE MESOTHELIUM, PLEURAL MESOTHELIOMA AND PULMONARY ADENOCARCINOMA

Malignant mesotheliomas are known to produce hyaluronic acid, in contr ast to most pulmonary adenocarcinomas which produce neutral mucin. CD4 4H is the major cell surface receptor for hyaluronic acid. The aim of this study was to investigate immunohistochemically the expression of this antigen in reactive mesothelium, pleural mesothelioma and pulmona ry adenocarcinoma and to assess its diagnostic utility in distinguishi ng the two tumours. Diffuse and intense membranous CD44H immunoreactiv ity was seen in 15 of 20 (75%) mesotheliomas and in all 20 biopsies of reactive mesothelium. In contrast, focal (<10% tumour) expression of CD44H was seen in only three of 20 (15%) pulmonary adenocarcinomas. We advocate the use of CD44H as a positive mesothelial marker for incorp oration alongside other established immunohistochemical markers used t o distinguish mesothelioma from adenocarcinoma.