(i) Detailed collection of clinical information: 1. Age: very important. Some tumors have good incidence age and rarely overlap. For example, liposarcoma is more common in adults, lipoblastoma is more common in young children (without paying attention to the age is easy to be misdiagnosed as liposarcoma); pleomorphic malignant fibrous histiocytoma is not seen in young children, found in young children pleomorphic sarcoma should be considered as other pleomorphic tumors may occur in children; neuroblastoma and hemangiomatous fibroblastic histiocytoma occurring in childhood. 2, the depth of the occurrence of the site: in addition to the bulging cutaneous fibrosarcoma, epithelioid sarcoma, smooth muscle sarcoma and hemangiosarcoma can occur in superficial soft tissues, including the dermis, most of the sarcomas occur in the deep soft tissues. For example, although atypical fibro-yellow tumor occurring in the skin has malignant characteristics and resembles malignant fibrous histiocytoma, it seldom recurs and metastasizes, so it should not be easily diagnosed as a sarcoma; another example is pleomorphic liposarcoma, although the tumor cells have polymorphism and a certain degree of anisotropy, it occurs in the subcutaneous area and has benign biological behaviors, so it should not be diagnosed as a liposarcoma. However, tumors of this form occurring in the retroperitoneum should be considered as low-grade malignant liposarcoma. In addition, it should be noted that carcinoma or melanoma can also metastasize to soft tissues, but it often metastasizes to superficial soft tissues and forms small nodules, and rarely metastasizes to deep soft tissues to form large masses. 3.Growth speed: malignant tumors of soft tissue grow faster than benign tumors. However, if one week – three weeks of faster growth of superficial nodules are mostly reactive hyperplastic lesions, even if the histomorphology is very similar to sarcoma, can not be easily diagnosed as sarcoma, nodular fasciitis is a good example. Soft tissue sarcomas can also grow slowly and then suddenly accelerate, either due to accelerated growth of the tumor itself or due to hemorrhage, necrosis, or cystic degeneration that causes the tumor to suddenly grow in size. The sudden growth of benign tumors does not necessarily mean that they are malignant and should be noted. 4. Others: gender, location, single or multiple, primary or recurrent, family history, etc. are all important. (ii) In-depth pathological observation: by naked eye, pay attention to the size of the tumor, whether the boundary is clear or not, whether there is any peripheral membrane formation, the depth of the tumor site (intradermal, subcutaneous, fascia, intramuscular, etc.), the texture, the presence of hemorrhage, necrosis, and the degree of necrosis. In addition to observing the location and depth of the tumor under the microscope, attention should be paid to the growth pattern and the following points: 1. Cell morphology: generally four kinds, spindle-shaped, round, epithelioid, and pleomorphic. Spindle-shaped cells are mostly seen in fibrosarcoma, smooth muscle sarcoma, spindle cell rhabdomyosarcoma, spindle cell liposarcoma, synovial sarcoma, malignant peripheral nerve sheath tumor, myofibroblast sarcoma, etc.; small rounded cells can be seen in embryonic and vesicular rhabdomyosarcoma, neuroblastoma, extraskeletal Ewing’s sarcoma, primitive neural ectodermal lobe tumors, round-cell liposarcoma, mesenchymal chondrosarcoma, malignant vascular Epithelioid cells can be seen in vesicular soft tissue sarcoma, epithelioid sarcoma, epithelioid hemangioendothelioma, epithelioid hemangiosarcoma, epithelioid smooth muscle sarcoma, malignant rhabdomyosarcoma, malignant mesothelioma, synovial sarcoma, epithelioid peripheral neurosarcoma, and extraskeletal mucinous chondrosarcoma. Polymorphic cells can be seen in malignant fibrous histiocytoma, pleomorphic rhabdomyosarcoma, pleomorphic smooth muscle sarcoma, pleomorphic liposarcoma, pleomorphic malignant peripheral nerve sheath tumor and so on. 2.Direction of cell differentiation and degree of differentiation: High-power consultation observation. For example, in rhabdomyosarcoma, the differentiation characteristics of rhabdomyoblasts can be seen as myofilament bundles appearing around the nucleus or forming transverse stripes; liposarcoma can be seen as the differentiation characteristics of lipoblasts containing single or multiple lipid droplets; smooth muscle sarcoma can be seen as the differentiation characteristics of smooth muscle cells with the nucleus bluntly rounded on both sides and the longitudinal arrangement of myofilaments visible in the cytoplasm; hemangiosarcoma can be seen as the tendency of the tumor cells to form the lumen of the vessel to varying degrees; interstitial chondrosarcoma in poorly-differentiated cells; and the tendency of the differentiated cells to form the lumen of the vessel to different degrees. In angiosarcoma, there is a tendency for tumor cells to form vascular cavities to varying degrees; in mesenchymal chondrosarcoma, there is the formation of islets of cartilage on the background of poorly differentiated cells; in soft tissue chondrosarcoma and osteosarcoma, it is more likely to see the characteristics of the corresponding differentiation to cartilage and bone; even in poorly differentiated neuroblastomas, the filamentous meshwork of dendritic synapses formed between the cells and the differentiation to ganglion cells can be seen at times. And the degree of differentiation can be determined according to the number of differentiated cells and the size of anisotropy, so as to judge the degree of malignancy and prognosis of the tumor. Note that not all soft tissue tumors can be judged under light microscopy to determine the direction of differentiation and differentiation, which can be done with the help of immunohistochemistry and electron microscopy. It is also important to note that when a certain tumor infiltrates muscle or fat tissue, some fat cells or myoblasts may remain in the tumor tissue, which may resemble adipoblasts or rhabdomyoblasts morphologically, so don’t misidentify them. For example, some benign tumors, such as pleomorphic smooth muscle tumor, pleomorphic lipoma and degenerative nerve sheath tumor, etc., due to the degeneration of the nucleus is dark stained with strange nuclei, but the structure of the nucleus is ambiguous, and the nuclear division is not seen. Under high magnification microscope, the number of nuclear divisions should also be noted, especially whether there are pathologic nuclear divisions. Arrangement structure: vesicular arrangement can be seen in vesicular soft tissue sarcoma and vesicular rhabdomyosarcoma; glandular cavity-like arrangement can be seen in synovial sarcoma, mesothelioma, nerve sheath tumor, malignant peripheral nerve sheath tumor; biphasic differentiation can be seen in synovial sarcoma and mesothelioma; cord-like arrangement can be seen in epithelioid hemangioendothelioma, extramedullary mucinous chondrosarcoma, epithelioid malignant peripheral nerve sheath tumor, round cell liposarcoma (rare). (rare). Fascicular arrangement can be seen in tumor-like fibrous tissue hyperplasia (ligamentous tumor), fibrosarcoma, malignant peripheral nerve sheath sarcoma, synovial sarcoma; endocrine-like arrangement (cellular z) can be seen in paraganglioma, vesicular soft-tissue sarcoma; lobular nodular nest-like arrangement can be seen in lipoblastoma, liposarcoma, epithelioid sarcoma, clear-cell sarcoma, infantile fibrous malignant tumors, nerve sheath mucocele; fence arrangement can be seen in in nerve sheath tumor, malignant peripheral nerve sheath membrane tumor, smooth muscle sarcoma, malignant salamander tumor (rare), synovial sarcoma (rare); clumped arrangement can be seen in neurofibroma, nerve sheath tumor, clumped fibrous histiocytoma; clumped capillary arrangement can be seen in the mucinous type of liposarcoma, mucinous type of malignant fibrous histiocytoma; angioepitheliomatous arrangement can be seen in the hemangioepithelioma, synovial sarcoma, interstitial chondroma, smooth muscle sarcoma, smooth muscle sarcoma; angiogranulomatous arrangement can be seen in the angioepithelioma, synovial sarcoma, interstitial chondrocyte sarcoma, synovial sarcoma, mesenchymal chondrosarcoma, smooth muscle sarcoma, malignant peripheral nerve sheath tumor, tumor-like myofibroblastic hyperplasia, glomerular paraganglioma, isolated fibrous tumors of the pleura and peritoneum, and liposarcoma (rare); daisy-chromatoid or pseudo-daisy-chromatoid arrangement can be seen in neuroblastoma, primitive neural exophyma, neuroblastoma-like nerve sheath tumor, and malignant peripheral nerve sheath tumor (rare); spoke arrangement can be seen in bulging cutaneous fibrosarcoma Fibrous histiocytoma, malignant fibrous histiocytoma, dedifferentiated liposarcoma, malignant peripheral nerve sheath meningioma, neurofibroma, neuroectodermal tumors = extracranial meningiomas; tubular – papillary arrangement can be seen in the mesothelioma, extra-vertebral canal ventricular meningioma. 4.Mesenchymal changes: note the number and nature of mesenchyme. Some benign or malignant soft tissue tumors have a large amount of mucus-like material between tumor cells, such as mucinous tumor (skin, intramuscular), mucinous neurofibroma, nerve sheath mucinous tumor, mucinous liposarcoma, mucinous chondrosarcoma, mucinous malignant fibrous histiocytoma, mucinous rhabdomyolysis cutaneous fibrosarcoma, mucinous smooth muscle sarcoma and so on. Tumors with mucinous transformation generally grow more slowly. A large number of collagen fibers in the tumor interstitium is also common in slow-growing tumors, but there are also highly malignant tumors with a large number of collagen fibers in the interstitium, such as synovial sarcoma, malignant fibrous histiocytoma, and post-irradiation sarcoma. Attention should also be paid to the presence or absence of calcification, pyogenic cartilage and bone formation, which is informative in the diagnosis of certain sarcomatoid lesions and tumors, such as ossifying myositis, calcifying tenosynovial fibroma, ossifying fibromucinous tumor, soft tissue osteosarcoma and chondrosarcoma, and extraskeletal mucinous-like chondrosarcoma.