Wolffian adnexal tumor (WAT) is a rare neoplasm believed to originate from wolffian remnants on the basis of its location in areas where these remnants are abundant. To study its histogenesis, the immunoprofile of 25 WATs was compared with that of 10 cervical and vaginal mesonephric remnants and 12 rete ovarii. WATs were unilaterally located in the broad ligament (n = 10), mesosalpinx (n = 9), ovarian hilus (n = 5), and pelvis, not otherwise specified (n = 1). They showed varying morphologies with solid (spindle cells), tubular (lined by columnar cells), retiform and multicystic (spaces lined by cuboidal and attenuated cells) patterns. WATs were immunoreactive for pan-cytokeratin (AE1/3, CK1) (100%), CAM 5.2 (100%), cytokeratin 7 (CK7) (88%, focal staining), keratin 903 (17%), epithelial membrane antigen (EMA) (12%), estrogen receptor (28%), progesterone receptor (24%), androgen receptor (78%), inhibin (68%), calretinin (91%), and vimentin (100%). No immunostaining was detected with monoclonal carcinoembryonic antigen and cytokeratin 20. The pattern of staining was nearly identical to that of the rete ovarii and differed somewhat from mesonephric remnants, which were diffusely immunoreactive for CK7, immunopositive for EMA (apical staining), and nonreactive for inhibin. Our findings provide immunohistochemical support for the derivation of WATs from wolffian remnants, in particular from the rete ovarii. Because of immunoreactivity for inhibin and calretinin in a significant number of WATs, our results further show that these immunostains alone do not allow absolute distinction of WATs from sex cord-stromal tumors and adenomatoid tumors, respectively, with which they may be confused.