Aggressive angio-mucinous tumor (AAM) is a benign tumor with unique clinical and biological behavior and locally aggressive characteristics, characterized by local infiltrative growth, high local recurrence rate and no distant metastasis. To date, only nearly 100 cases have been reported abroad, and only 10 cases have been reported in the domestic literature. The first case of AAM was reported by Steeper and Rosai [1] in 1983, and the disease mostly occurred in the vulva, perineum, pelvis and inguinal region in adult women. Chan et al [2] statistically reported 106 cases with a male to female ratio of 1:6.6. The disease has a high recurrence rate, with Nakamura et al [3] statistically reporting a local recurrence rate of 33% to 83% and a recurrence time from 6 months to 14 years after surgery. 71% recurrence rate within 3 years is mostly thought to be related to incomplete surgical excision [2 ]. The disease occurs more frequently in men in the scrotum, bladder and spermatic cord. The tumor sites are closely related to the genitourinary system, and the following tumors have been reported: 4 cases in the bladder (including the one reported here), 1 case in the pelvis with tumor invading the bladder, 9 cases in the scrotum, 5 cases in the spermatic cord and pars seminis (including the one reported here), and 1 case in the prostate reported by Yang Shunliang et al [4]. Tumors occurring in the genitourinary system are generally large in size, with the largest reported tumor reaching 40 cm x 20 cm and weighing 19.8 kg, and often present with clinical symptoms related to the genitourinary system. It is a tumor composed of mesenchymal cells, and it has been suggested that this tumor is a low-grade sarcoma, the etiology and pathogenesis of which are still unclear. A recent study by Martines et al [5] suggested that the disease arises from the differentiation of perivascular stem cells with multidirectional differentiation potential. It has been found that the tumor occurs mostly in women of childbearing age and that the tumor expresses estrogen and progesterone receptors, suggesting that it is a hormone-responsive tumor [6, 7]. The tumor is mostly poorly demarcated from the surrounding tissues and often infiltrates into the adjacent fibrofatty tissue. AAM mostly shows slow, insidious growth and lacks clinical specificity, and is often difficult to differentiate from other benign diseases such as Bartholin’s gland cyst, hernia, pelvic abscess, bladder, spermatic cord and intra-scrotal tumors, making preoperative diagnosis more difficult. Ultrasound and CT can only indicate the size and location of soft tissue masses, and the demarcation between tumor and surrounding tissues is not clear. It is also important for defining the extent of the tumor, its relationship with the surrounding tissues and organs, and determining the recurrence of the tumor. Pathologically, the tumor is generally grayish-yellowish-brown in color, soft and gel-like in texture, without necrosis or cystic changes. Histologically, the tumor shows spindle-like or stellate cell proliferation separated by a loose fibrous mucus-like stroma with scattered blood vessels of different sizes, some of which are hyperplastic or glassy in the wall. Immunohistochemistry: Fetsch [6] performed immunohistochemistry in a group of 29 patients with AAM, Desmin(+) 22/22, SMA(+) 19/20, MSA(+) 16/19, Vimentin(+) 17/17, CD34(+) 8/16, estrogen receptor(+) 13/14, progesterone receptor(+) Some tumor cells contained a large amount of eosinophilic cytoplasm, and the combination of immunohistochemistry suggested that their myofibroblast or fibroblast origin was likely. For pelvic, perineal and genitourinary-related masses, they should be differentiated from benign tumors with low recurrence rate, such as angiomyofibroblastoma, angiofibroma of cells and lipoma, in addition to malignant mucinous tumors with metastatic potential. Although the biological nature of the disease is benign, the disease is locally aggressive and has a high recurrence rate by simple excision. Therefore, for the first diagnosis and local recurrence of the tumor, the better treatment is local expanded excision of the lesion, and complete excision can significantly improve the cure rate and reduce the recurrence rate. The high recurrence rate is attributed to incomplete surgical resection. For pelvic and perineal masses with unclear preoperative diagnosis, intraoperative frozen section examination should be done to clarify the diagnosis and avoid re-expansion surgery after surgery. Some people believe that lymph node dissection and radiotherapy and chemotherapy are meaningless in the absence of distant and lymph node metastases in AAM. Rhomberg et al [9] concluded that for tumors with multiple recurrences or difficult local excision, radiotherapy combined with the application of the radiosensitizer propionamide is effective. For larger tumors, complete resection is difficult because the tumor tissue is indistinguishable from normal connective tissue, and preoperative angiographic embolization can improve the effect of surgical resection. In addition, preoperative external irradiation and intraoperative electron beam radiotherapy have been reported to reduce the rate of local recurrence. As an adjuvant therapeutic measure, the application of anti-estrogenic drugs has a role in avoiding local recurrence after surgery [10]. A case of multiple recurrence of vulvar AAM with tumor disappearance in 3 months by applying GnRH analogs was reported; a patient with pelvic AAM was treated with LH-RH analogs with remarkable results. However, because of the small number of cases treated so far, the treatment regarding hormonal aspects has to be further explored. The tumor is locally infiltrative and prone to recurrence, so complete surgical resection can avoid recurrence and long-term follow-up with imaging is necessary.