On December 11, Ms. Gui, who lives in Lijia, came to the pediatric gynecology department of Changzhou Children’s Hospital with her 10-month-old daughter, telling that her daughter had interstitial vaginal bleeding for 8 months. She had an anemic appearance, no enlargement of both breasts, no pigmentation changes in the areola, a young girl type vulva with dark red blood stains, no inflammatory discharge on the surface, no rupture, normal urethra and vaginal opening, and no tissue prolapse from the vaginal opening. Anal examination: A mulberry-like mass was palpated at about 2CM from the vaginal orifice, and dark red blood flowed from the vagina when the mass was pushed towards the vaginal orifice, but no tissue protrusion was seen. The day before the report came out, Ms. Gui found flesh-like tissue on the child’s urine film, so she sent the child to the hospital for pathological examination (I reminded her when asking for medical history whether there was anything coming out, and if so, pathological section could be done to help the diagnosis). On December 18, the AFP report was 536ng/ml, which was significantly elevated. We immediately communicated with the parents and helped the child to be admitted to the pediatric oncology ward as soon as possible. The diagnosis was clear, and chemotherapy was started on December 27. Vaginal endodermal sinus tumor is a relatively rare and highly malignant germ cell tumor that occurs mainly in infants and children under the age of 3. In children, endodermal sinus tumors occur in the gonads and sacrococcygeal region, but are rarely located in the vagina. Extragonadal endodermal sinus tumors are caused by the migration of embryonic primordial germ cells from the germinal ridge of the yolk sac endoderm, or by the legacy of tumorization. Because of its high malignancy, it usually dies within 2-4 months of diagnosis if left untreated. Therefore, early diagnosis is the key to improve the outcome. Intermittent bloody vaginal discharge is the most common and even the only clinical manifestation, although it is easily detected and noticed by parents. However, most parents do not pay enough attention to it because of lack of medical knowledge, and some parents do not pay attention to it until they find tumor tissue in the vagina, which delays the valuable time for early diagnosis and treatment. How to raise parents’ awareness of the potential risks of vaginal bleeding in children is the key to early diagnosis and improved outcome, and deserves the attention of our medical professionals and caregivers. Serum AFP screening and anal examination should be performed to rule out the disease in infants and children with vaginal bleeding, so that early diagnosis and treatment can be achieved. In the early 1970s and before, vaginal endodermal sinus tumors were mainly treated with radical local surgery and radiotherapy, with a very poor prognosis and a 2-year survival rate of less than 10.0%. after the 1970s, combined chemotherapy played a very important role in the treatment of vaginal endodermal sinus tumors, and the survival rate of patients treated with chemotherapy increased significantly. This treatment modality is a major breakthrough in the treatment of vaginal endodermal sinus tumors, which not only treats the tumor and improves the prognosis, but also has the advantages of fewer complications and fewer sequelae compared to radical surgery and radiotherapy. More importantly, chemotherapy can preserve the patient’s reproductive function, making it a more ideal treatment of choice for vaginal endodermal sinus tumors. Causes of vulvovaginal bleeding in infants and children: severe vulvovaginal infection, vulvovaginal injury, vaginal foreign body, urethral mucosa prolapse, genital tract tumor and precocious puberty, etc. Parents should seek medical attention if they find blood on their children’s underwear or diapers.