RESUMEN
BACKGROUND: The placental site trophoblastic tumor is the second rarest tumor of trophoblastic disease, with less than 300 cases reported. Clinical presentation it's a diagnostic challenge, it has an unpredictable malignant potential, and it can develop choriocarcinoma and even have simultaneous presentation. CASE REPORT: We present the case of a 34 year old woman with chronic transvaginal bleeding since her last cesarean (five months ago), with histologic diagnosis of placental site trophoblastic tumor and inmuno- histoquimic report of choriocarcinoma, this early diagnosis improves her survival prognostic. CONCLUSION: placental site trophoblastic tumor and their evolution to choriocarcinoma have a low rate but it's possible. That it's the reason why complete diagnosis with biopsy, histologic and inmunohistoquimic report is mandatory to improve therapeutic.