Functional thrombomodulin expression on epithelial skin tumours as a differentiation marker for suprabasal keratinocytes

Abstract

In normal human skin,, immunoreactive thrombomodulin (TM) is expressed in a strict differentiation related pattern, solely in suprabasal spinous layer keratinocytes. To evaluate the potential application of TM as a differentiation marker for keratinocyte-derived skin tumours, we have studied immunohistopathological, biochemical and functional TM activities in various skin tumours. Immunoreactive, full sized and enzymatically active TM was expressed in keratinocyte-derived skin tumours (squamous cell carcinoma, seborrhoeic keratosis and partly Bowen's disease), as well as normal epidermal keratinocytes and endothelial cells. However, no TM was detected in basal cell carcinomas, senile keratosis or non-squamous epithelial tumours such as malignant melanoma, naevus pigmentosus and Paget's disease. Interestingly, decreased expression was observed in verruca vulgaris. These findings suggested that differentiation-dependent TM expression was restricted to epithelial skin tumours and undetectable on neural crest derived tumours. TM is a differentiation marker for spinous layer keratinocytes and is a useful tool in histopathological study of epithelial tumours.

Expression and activity of thrombomodulin in human gingival epithelium: in vivo and in vitro studies

“…Gingival epithelium is a strati®ed squamous and dierentiating tissue that consists of 4 strata; the basal, spinosum, granulosum and corneum (27). Within the epidermis, the TM±DAB reaction product is limited to keratinocytes in the basal and spinous layer, suggesting that TM is induced when basal keratinocytes begin to terminally dierentiate (7,8,28). The TM±DAB reaction product that we observed in the gingival epithelium corresponded to previous ®ndings in the epidermis (Fig.…”