BACKGROUND: Although the clinical picture of endometrial stromal sarcoma (ESS) is variable, it was never reported to present as a postpartum hemorrhage. In addition, ESS is a tumor type of which, due to its rarity, little is known regarding chemosensitivity and genetic changes. CASE: A 28-year-old woman complaining of persistent postpartum bleeding was referred to our hospital, where she was diagnosed with ESS. At laparotomy, the invasion of nervous and vascular pelvic structures rendered her inoperable, and chemotherapy (doxorubicin 50 mg/m(2) for 15 min; ifosfamide 5 g/m(2)/24 h; mesna 5 g/m(2), every 3 weeks) was initiated. The ESS appeared to be chemosensitive because after three treatment cycles the tumor iliac metastase significantly decreased in volume and became surgically removable. Chemosensitivity was confirmed microscopically. Three additional courses of chemotherapy and pelvic irradiation were administered. Cytogenetic evaluation of both the primary as well as the metastatic lesions revealed a t(10;17)(q22;p13) as the sole cytogenetic abnormality. CONCLUSIONS: Three interesting features of this particular case put ESS in a new perspective. First, the fundal ESS permitted normal conception and pregnancy but caused a postpartum haemorrhage. Second, the ESS was clearly chemosensitive. Third, we report a novel cytogenetic aberration in ESS, the molecular characterization of which might lead to the identification of the deregulated pathway(s) triggering tumor development in ESS.