Background. The low incidence of ovarian adenosarcomas explains the paucity of available data regarding their biologic markers. Our aim was to investigate the presence of CD10, estrogen and progesterone receptors (ER and PR) in these tumors. Case. Four cases of primary ovarian adenosarcoma were retrieved in our pathology databases. We assessed the immunohistochemical stainings for ER, PR and CD10 in 3 ovarian adenosarcomas without sarcomatous overgrowth (OAS), and 1 ovarian adenosarcoma with sarcomatous overgrowth (OAS-S). When considering the malignant stromal component, 2 OAS showed the presence of ER and PR, whereas the OAS-S was only ER positive. CD10 positivity was observed in the sarcomatous cells of all 3 OAS but was absent in the OAS-S. Conclusion. The identification of a hormone sensitive disease is the main clinical implication of this study. Moreover, the current results add OAS to the list of CD10 positive ovarian tumors. Background. The low incidence of ovarian adenosarcomas explains the paucity of available data regarding their biologic markers. Our aim was to investigate the presence of CD10, estrogen and progesterone receptors (ER and PR) in these tumors. Case. Four cases of primary ovarian adenosarcoma We assessed the immunohistochemical stainings for ER, PR and CD10 in 3 ovarian adenosarcomas without sarcomatous overgrowth (OAS), and 1 ovarian adenosarcoma with sarcomatous overgrowth (OAS-S). When considering the malignant stromal component, 2 OAS showed the presence of ER and PR, but the OAS-S was only ER positive. CD10 positivity was observed in the sarcomatous cells of all 3 OAS but was absent in the OAS-S. Conclusion. The identification of a hormone sensitive disease is the main clinical implication of this study. Moreover, the current results add OAS to the list of CD10 positive ovarian tumors.