Distribution of keratins in normal endothelial cells and a spectrum of vascular tumors: Implications in tumor diagnosis

Vascular endothelial cells are specialized mesenchyme-derived epithelial-li ke lining cells which are the essential participants in benign and, maligna nt vascular tumors. Although endothelia in lower animals often express kera tins (K), human endothelia are generally K negative and vimentin-positive. However, K expression has been noted in Some endothelia and in some epithel ioid vascular tumors. In this study, we systematically examined normal huma n vascular endothelia and a spectrum of human vascular tumors (n = minimum of 137 tumors with each marker) for simple epithelial keratin polypeptides of the Moll catalogue (K7, K8, K18, and K19). Selected vascular tumors were also evaluated with antibodies to K14 and the monoclonal antibody 34 beta E12 that recognizes several keratins of stratified epithelia. Endothelia of normal veins, venules, and lymphatics commonly exhibited focal positivity for K7 and K18, whereas K8, K14, and K19 were not seen in non-neoplastic en dothelia with the antibodies used. Lymphangiomas (6 of 7) and venous hemang iomas (6 of 13) often showed K7-positive endothelial cells; K18 was detecte d less commonly, whereas K8 and K19 were not detected. Epithelioid hemangio endotheliomas (EHEs) showed K7 and K18 expression in the majority of cases (50% and 100%, respectively), while K8 was seen in 10% cases and K14 and K1 9 in none. In contrast, epithelioid angiosarcomas (EAs) were often positive for K8 and K18 (approximately 50%), whereas they less commonly showed K7 a nd only occasionally K19; all tumors were negative for K14 and with the ant ibody 34 beta E12, Nonepithelioid angiosarcomas (AS) less commonly showed k eratin expression with K7, K8, and K18 being positive in 20% of cases, and K14 and K19 in none of the cases. Epithelial membrane antigen (EMA) was occ asionally detectable in EHE (2/19) but was present in 4 of 16 (25%) EAs and 17 of 48 (35%) nonepithelioid AS. These findings document the common prese nce of focal reactivity for K7 and K18 in subsets of normal endothelia and also the frequent presence of simple epithelial keratins in malignant vascu lar tumors, while such expression is uncommon in nonepithelioid angiosarcom as. K- and EMA-positivity in neoplastic endothelia needs to be considered i n the evaluation of human tumors. K antibodies such as those specific to K1 9 or AE1 that do not react with K8 and K18 should be used in the differenti al diagnosis of epithelioid vascular tumors and carcinomas. Copyright (C) 2 000 by W.B. Saunders Company.