Swellings of soft tissues, in the absence of evident signs of infection, should be evaluated carefully, since soft tissue sarcomas are often deeply seated and may not be easily palpable. Deepness, firmness and fixity are suspicious signs. Deep sarcomas, especially those arising in the trunk, may origin in widely expandable sites and are generally very large at diagnosis. Unexplained deep pain should prompt the physician to consider a possible soft tissue origin in addition to a skeletal one, and skeletal X-rays are therefore insufficient to exclude a neoplastic cause for pain in such cases. An ultrasonogram can confirm the presence of a clinically doubtful soft tissue mass.
More expensive exams are computerized tomography scan and magnetic resonance.
Both have the advantage of being useful as staging presurgical exams, while ultrasound must be followed by one of the two if a tumor is confirmed. Computerized tomography and magnetic resonance scans are roughly equivalent, even if magnetic resonance can give coronal and sagittal views in addition to transaxial ones, and may better contrast muscles and vessels. The execution either of computerized tomography or of magnetic resonance is therefore recommended preoperatively. A biopsy is recommended of virtually all soft tissue masses not known to the physician or the patient to be unchanged from years before. It is recommended that biopsy is planned by a surgeon involved in the treatment of soft tissue sarcomas .