[Evaluation of the differences of opinion in the histopathologic diagnosis of soft tissue tumors].

Evaluation of observers variation in the histopathologic diagnosis of soft tissue tumors. 260 cases of soft tissue tumors referred to the CTRC (Canadian Tumour Reference Center) for diagnostic opinion were reviewed. These tumors were collected from 98 different hospitals within the 10 canadian provinces and had been submitted to a specialized panel of pathologists having a particular interest in this field. 22 tumors of nonmesenchymal origin have been discarded. The main problem posed by the contributors related to the histologic typing of overtly malignant and sarcomatous tumors (122/238). Comparing the diagnoses proposed by contributors and the panel, a consensus in term of benign and malignant tumor was reached in 89% of the cases. Within this panel, there was consensus in 84% of the cases. However, regarding the histologic typing, a consensus was reached between contributors and the panel in only 65% of the studied cases. Within the panel, there was a majority diagnosis in merely 62% of them. A mean of three different diagnoses were proposed for each case. A review of the literature shows that histologic typing of soft tissue tumors is of only limited prognostic significance. On the other hand, the clinical staging comprising histologic grade, size, depth, local growth and metastases is essential to establish prognosis and treatment. However, since certain tumors respond differently to treatment, a precise histopathologic diagnosis using immunohistochemistry and electron microscopy is mandatory.