Thymidine phosphorylase expression in normal and hyperplastic endometrium

Aims-To investigate the expression of thymidine phosphorylase (TP), a known angiogenic factor for endothelial cells, in normally cycling endometrium a nd various forms of endometrial hyperplasia. Methods-TP expression was assessed with the P-GF.44C monoclonal antibody, u sing the alkaline phosphatase anti-alkaline phosphatase method. Ninety two normal and hyperplastic endometria were studied. Results-In normal proliferative endometrium, TP is found exclusively in the basal layer and the inner third of the functionalis; expression is cytopla smic in glandular epithelium and nuclear in stromal cells. It is invariably patchy. This immunohistochemical picture remains almost unaltered during t he early and mid secretory phase of the normal menstrual cycle but, most im pressively, TP is expressed uniformly in the epithelium of all endometrial glands towards the end of the cycle. At this stage, expression is mixed nuc lear/cytoplasmic and there is very little stromal nuclear staining. In simp le endometrial hyperplasia, the staining pattern for TP is identical to nor mal proliferative endometrium, with a distribution that is usually limited to a few rather weakly proliferating glands and to the adjacent periglandul ar stroma of the deep endometrium. The distribution is more extensive in co mplex and atypical endometrial hyperplasias, where a mixed nuclear/cytoplas mic pattern usually prevails over the pure cytoplasmic reaction. Conclusions-TP is expressed consistently in normal and hyperplastic endomet rium, suggesting a role in physiological and pathological angiogenesis. In normal endometrium, TP has a definite pattern of distribution, which is dep endent on the phase of the menstrual cycle, whereas in all forms of endomet rial hyperplasia the enzyme is randomly distributed and lacks an orderly pa ttern.