Analysis of the vascular profile and CD99 protein expression in the partial and complete hydatidiform moles using quantitative CD34 immunohistochemistry.

BACKGROUND: Hydatidiform mole is a gestational trophoblastic disease with two different types: complete (CHM) and partial hydatidiform moles (PHM). The villous stroma of CHM is avascular or contains primitive endothelial-lined vascular elements. CD99 is a leukocyte antigen expressed in both normal and neoplastic tissue.

OBJECTIVES: To examine the expression of CD99 and vascular profile in PHM and CHM compared to first trimester pregnancy termination (TOP).

MATERIALS AND METHODS: Fifty trophoblastic tissue specimens were immunostained using monoclonal antibodies decorating CD99 and CD34 antigens (vasculogenesis). CD99 expression and the vascular parameters were scored.

RESULTS: In CHM and PHM, the number of blood vessels with distinct lumens in the villous stroma (centrally and peripherally located) was significantly reduced (p<0.05), compared to TOM. In CHM, the number of the centrally located hemangiogenetic cords was higher compared to TOP. No statistically significant differences were found between CHM and PHM. In chorionic villi of TOP, a strong CD99 reactivity was seen in the endothelial, decidual, fibroblastic and in trophoblastic cells (syncytiotrophoblasts and cytotrophoblasts). Weak to virtually absent CD99 reactivity was seen in the trophoblastic cells of chorionic villi with molar changes.

CONCLUSIONS: Vasculogenesis can be initiated in the molar pregnancies despite the absence of embryos or maternal derived chromosomes. CD99 may have a possible role in the development of molar changes.