BACKGROUND: Given the paucity of data regarding hormone dependency, it was the purpose of this study to screen for the presence of estrogen and progesterone receptors in uterine adenosarcoma (UAS). METHODS: One hundred and five centers were asked to screen their files for uterine adenosarcomas. A immunohistochemical estrogen and progesterone receptor determination was performed. RESULTS: Twenty-eight primary UAS were stained, including one cervical adenosarcoma. Sarcomatous overgrowth could be observed in eight. Furthermore, two cases of recurrent UAS, one only consisting of endometrial stromal sarcoma, were stained. UAS lacking sarcomatous overgrowth showed estrogen receptor positivity in 17/20 (85%) and 16/20 (80%) in the epithelial and sarcomatous component, respectively. Progesterone positivity was observed in 13/20 (65%) and 12/20 (60%) in the epithelial and sarcomatous component, respectively. In 18/20 (90%) of the cases, either the estrogen or the progesterone receptor stained positive in the sarcomatous component. UAS with sarcomatous overgrowth showed estrogen receptor positivity in 4/8 (50%) and 0/8 (0%) in the epithelial and sarcomatous component, respectively. Progesterone positivity was observed in 2/8 (25%) and 1/8 (12%) in the epithelial and sarcomatous component, respectively. The stromal component of both recurrent cases stained moderately positive for estrogen receptor whereas progesterone receptor was considered negative. CONCLUSION: The observation that the sarcomatous component of UAS without sarcomatous overgrowth frequently expresses hormone receptors might be of significant clinical importance.