Placental site trophoblastic tumor (PSTT) refers to a specific type of relatively rare trophoblastic tumor that originates from the placental implantation site. It is generally benign, but can also be malignant. The tumor is solid, usually confined to the uterus, mostly protruding into the uterine cavity, growing in the form of polyps, or invading the muscular layer or even penetrating the uterine wall. The tumor is white or yellow in color, soft in texture, and small bleeding foci are occasionally seen. PSTT is mainly composed of intermediate cells under the microscope. The tumor cells are round, polygonal or spindle-shaped, with abundant cytoplasm and heterogeneous staining, and nuclear schizophrenia is rare. There is no extensive hemorrhage or necrosis, and there is no villous structure. The tumor cells can produce HCG and HPL (human placental lactogen). Clinical manifestations: 1. History Usually secondary to full-term birth (or preterm birth), miscarriage or gravidity, or coexisting with pregnancy. 2. 2. Symptoms The main manifestation is irregular vaginal bleeding, sometimes amenorrhea, which may be accompanied by anemia. In a few cases, metastatic symptoms are the first symptom, and the metastatic site is mainly lung, or multiple metastatic lesions via bloodstream. 3. Gynecological examination The uterus may be uniformly or irregularly enlarged. It is usually as large as 8 to 16 weeks. Diagnosis The diagnosis of PSTT must rely on pathology. It is characterized by: 1. single type of intermediate trophoblast, lack of typical cytotrophoblast and syncytial trophoblast, no villous structure, hemorrhagic necrosis is less common; 2. immunohistochemical staining, most tumor cells are HPL positive and only a few are HCG positive. PSTT can be diagnosed clinically by scraping specimens, but for accurate determination of the depth of PSTT erosion into the myometrium, hysterectomy specimens must be relied upon. Blood β-HCG may be mildly elevated or normal, and blood HPL may be mildly elevated. B-mode ultrasound shows hypoechoic areas within the myometrium. Color Doppler ultrasound can show rich blood flow and low impedance blood flow image at the tumor site. Differential diagnosis: 1. Intrauterine scrapings of indolent miscarriage include fetal sac and chorionic villi. 2. Choriocarcinoma has typical cytotrophoblast and syncytial trophoblast, often accompanied by massive bleeding and necrosis. 3, syncytial cell endometritis There is syncytial cell infiltration in the superficial muscular layer of the placental area, mixed with unequal amounts of inflammatory cells. 4.When the tumor cells of PSTT are shuttle-shaped, it should be distinguished from smooth muscle sarcoma. PSTT has less nuclear division and its clinical manifestations are different from smooth muscle sarcoma. V. Prognosis Most PSTTs are benign, only 10%-15% have poor prognosis. The prognostic factors affecting PSTT are: 1) poor prognosis if the interval between the first pregnancy and clinical diagnosis is >2 years; 2) metastasis is likely to occur if the first pregnancy is full-term; 3) poor prognosis if the nuclear schizophrenia is high, especially if it is accompanied by extensive hemorrhagic necrosis; 4) poor prognosis if the metastasis is outside the uterus. Treatment Surgery is the treatment of choice for PSTT. The scope of surgery is total hysterectomy and bilateral adnexal resection. The ovaries can be preserved in young patients. Because intermediate trophoblasts are not sensitive to chemotherapy, they are only used for postoperative adjuvant treatment of extrauterine metastases. Regimens such as MAC, PVB or EMA/CO are commonly used. Radiotherapy can be used for single metastases or locally recurrent lesions.