EXPRESSION OF PLACENTAL PROTEINS IN COMPLETE AND PARTIAL HYDATIDIFORMMOLES

Examination of routinely stained haematoxylin and eosin sections may s ometimes prove inadequate in differentiating partial hydatidiform mole s (PHM) from complete hydatidiform moles (CHM). While cytogenetic anal ysis can aid in the distinction, such facilities are not always availa ble. The possibility of using immunohistochemistry to aid in the diffe rentiation was studied. Twenty-five histologically proven CHM and 11 P HM were studied for their patterns of expression of human chorionic go nadotrophin (hCG), human placental lactogen (hPL) and placental alkali ne phosphatase (PIAP). All CHM stained diffusely with hCG and focally with both hPL and PIAP irrespective of gestational age. Of PHM, 63.6% were diffusely positive for hCG, 27.3% for hPL and 54.5% for PIAP; the rest were focally positive. The hCG pattern changed from diffuse to f ocal with increasing gestationai age of PHM, while those of hPL and PI AP became increasingly diffuse with gestational age. While these prote in expressions may be applied in differentiating tale PHM from CHM, it is not useful in first trimester cases. The most helpful application is that focal expression of hCG and diffuse expressions of hPL and PIA P is not seen in CHM, thereby excluding such a diagnosis. PHM, in cont rast, can show either diffuse or focal expression of all 3 antigens.