Adenomatoid tumors of the female genital tract: Immunohistochemical study of CD34 and factor XIIIa in eight cases

Adenomatoid tumors (ATs) are benign lesions usually arising within the muscularis of the fallopian tube and uterus. Mesothelial differentiation has been demonstrated in ultrastructural and mucin histochemical studies. CD34+ dendritic interstitial cells are putative multipotential precursor cells present in most mesenchyme. Factor XIIIa+ histiocytes are also present in most connective tissue and are increased in tissues undergoing stromal remodeling. To further characterize the morphogenesis of AT, we examined 8 female genital ATs for the presence of dendritic fibroblasts that express the human progenitor cell antigen CD34 and for dendritic stromal histiocytes that express coagulation factor XIIIa (FXIIIa). We also studied expression of cytokeratin AE1/AE3, muscle specific actin HHF35, and endothelial markers CD31 and von Willebrand factor. The normal myometrium and myosalpinx consists of actin+ myocytes richly invested with perimyseal CD34+ dendritic fibroblasts, vessels, and scattered small FXIIIa+ histiocytes. Submesothelial fibroblasts are also CD34+. Normal surface mesothelium is CD34 negative and keratin+. ATs have cytokeratin+ glands and vacuolated, plexiform, or cord-like structures in a collagenous stroma. In 6 AT, single or small clusters of mesothelium-like acini expressed CD34; however most AT acini were CD34 negative. Some AT glands were partly Lined by spindled CD34+ fibroblast-like cells. CD31 and anti-von Willebrand factor stained only vessels. Some AT had intraluminal plump FXIIIa+ histiocytes and FXIIIa+ dendritic cells were numerous in the collagenous stroma of some AT. Though the precise biological significance of the data remain speculative, our observations, taken with biochemical data on CD34 and FXIIIa, are consistent with the notion that multipotential CD34+ fibroblast-like interstitial cells in mullerian mesenchyme can undergo mesothelial differentiation to form AT and that FXIIIa+ stromal histiocytes may be involved in spreading and adhesion of stromal fibroblasts and in matrix remodeling during AT morphogenesis.