Endometrial Stromal Sarcoma Arising from Endometrial Polyp: A Case Report.

Endometrial stromal sarcoma (ESS) is a rare malignant tumor of the uterus. We report an uncommon case of ESS composed of both low-grade ESS and high-grade ESS arising from an endometrial polyp. On the findings of magnetic resonance imaging and contrast computed tomography, a patient was suspected of having uterine malignant tumor. She underwent a total abdominal hysterectomy with bilateral salpingo-oophorectomy. Macroscopically, the tumor was a polypoid lesion in the uterine cavity. The tumor was an endometrial polyp with ESS components. ESS was composed of low-grade ESS and high-grade ESS. By immunohistochemistry, both an endometrial polyp and low-grade ESS showed a positivity for CD10, estrogen receptor (ER), and progesterone receptor (PR). However, high-grade ESS showed only a focal and weak CD10 positivity with no immunostaining for ER and PR. A focal or diffuse positivity for α-smooth muscle actin and desmin was noted in both low-grade and high-grade ESS. The positive rates of Ki-67 and p53 in high-grade ESS were elevated up to over 95%. She was diagnosed as having ESS in a stage IA. After surgery, she received no further treatment. She has been without recurrence for 4 years since an initial surgery. In conclusion, immunohistochemical analyses are useful for make an accurate diagnosis of ESS showing a transition from low-grade ESS to high-grade ESS in addition to the conventional method.