Soft tissue sarcoma, compared to those common cancers, is less prevalent and usually less known. Here I will explain systematically what is soft tissue sarcoma? This malignant tumor is good at disguise and easy to hide. I. What is soft tissue sarcoma? Soft tissue is a mesenchymal tissue, which includes smooth muscle, transverse muscle tissue, adipose tissue, blood vessels, nerves, etc. In short, it is some mesenchymal tissue or even neuroectodermal tissue other than bone. Such tissues are called soft tissues, and tumors originating from these soft tissues are called soft tissue tumors. What is the incidence rate of soft tissue sarcoma? Although the incidence rate is low, the malignancy degree is not low. The incidence rate of soft tissue tumors is not high, accounting for about 1% of all tumors. There are many oh subtypes of soft tissue tumors, probably more than 50 subtypes. There are benign and malignant soft tissue tumors, benign ones are lipoma and fibroma, malignant ones become sarcoma. There are more types of sarcomas: smooth muscle sarcoma, rhabdomyosarcoma, liposarcoma, angiosarcoma or malignant peripheral nerve sheath tumor. Rhabdomyosarcoma, especially embryonal rhabdomyosarcoma, occurs in children under 10 years of age. Synovial sarcoma occurs in people between the ages of 20 and 40. Malignant fibrous histiocytoma is more common in middle-aged and older patients. Soft tissue sarcomas can develop in various locations throughout the body, with the lower extremities or buttocks being the most common. It can also occur in the trunk, upper limbs, scapular girdle, pelvis, and other areas. Usually we talk about cancer and do not know much about soft tissue tumors and do not pay enough attention to them. Although soft tissue malignant sarcoma accounts for 1% of all tumor incidence, the malignancy of sarcoma after lesion is as high as that of cancer! What is more serious is that sarcoma is more insidious in onset, early lumps are usually painless and do not affect patients’ life, but neglecting the change of its status will lead to its transformation from benign to malignant! In addition, we should pay special attention to the recent changes of the mass, such as whether it has grown, whether the skin temperature has increased, whether there are painful symptoms, whether there are mutations or ulcers on the surface, and if these conditions are found, we must go to the regular hospital. Consult a doctor. Usually, we do not deal with multiple cases that are considered to be like lipomas. However, if it is more than 5 centimeters in size and the patient has painful swelling, we recommend surgery to remove it. Therefore, if the size is more than 5 cm, regardless of benign or malignant, you must go to the hospital. 2.Imaging There are ultrasound, CT, MRI, and pet-ct, which are all very effective means. pet-ct is very effective for whether the tumor has systemic metastasis recurrence and whether there are multiple tumors. However, the shortcoming is that the cost is higher. Some primary hospitals do not pay enough attention to soft tissue tumors, and when they see a lump of 2 or 3 centimeters, they think it is relatively small and give it to be removed in outpatient surgery. Here, we deliberately emphasize the need to have an imaging diagnosis, such as ultrasound, CT or MRI, so that if it is removed in outpatient surgery and is malignant, we can remedy a surgery or radiotherapy afterwards, which can also play a role of marking and localization. Otherwise, it is easy to find the original bed of the tumor accurately due to the lack of preoperative imaging and the loss of the obvious boundary line of malignant sarcoma, which makes it more difficult for the patient in the subsequent treatment. 3.Biopsy There are two ways of biopsy, one is needle biopsy and the other is excisional biopsy. The biopsy will show whether it is benign or malignant. Because the treatment of benign and malignant means are different. The advantage of needle biopsy is that it is quicker and can be done on the same day, and the results are available in 2 hours. But the disadvantage is that the accuracy rate is not as high as that of excisional biopsy, which is about 85%. Therefore, we recommend that needle biopsy can be done for superficially located masses, but if the mass is deeper, a puncture should be performed under CT or B-ultrasound guidance. Besides, the advantage of excisional examination is that the accuracy rate is higher, but the disadvantage is that it takes longer time. Early symptoms of soft tissue tumor Many patients with retroperitoneal tumor visit the doctor because of symptoms such as back pain and lumbago, but it turns out that the tumor is at least 10 centimeters or more, without any obvious symptoms in the early stage.