The collaboration between the clinician and the pathologist is necessary for an optimal diagnosis and management of patients with soft tissue sarcoma. The clinician provides information about the patient and about the clinical aspect of the tumor. The pathologist gives a histological diagnosis, a grading of the tumor and information on the surgical margins. A staging of the tumor is then possible that will provide a prognosis for each tumor and will allow a stratification of patients with a similar prognosis and a comparison between treatments. A modification of the AJC (American Joint Committee on Cancer) staging system is proposed according to a better understanding of the different prognostic factors achieved during the last decade.