[Histopathological diagnostic concordance in bone and soft tissue sarcomas between two comprehensive cancer centers from eastern and western Europe: a collaborative experience].

INTRODUCTION: This study aims to assess the degree of concordance of histological diagnosis of bone and soft tissue sarcomas between a Comprehensive Cancer Center (CCC) of Eastern Europe - not specialized in this area of pathology - and an important CCC of Western Europe, which is one of the coordinators of a clinical reference network in sarcoma pathology. The goal is to have an overview of the sarcomatous pathology in a region of Eastern Europe and to discover diagnostic discrepancies between the two centers, while determining their cause.

MATERIALS AND METHODS: The initial diagnosis was compared with the revised diagnosis on 110 specimens from 88 patients with bone or soft tissue sarcomas from East-European CCC, in a one-year period of time.

RESULTS: Complete diagnostic agreement was observed in 55 cases (62.5%), a partial agreement in 23 cases (26.1%) and a major disagreement in 10 cases (11.4%). Major discrepancies of the histological type was observed in only 3 cases (3.4%): one case of discordance benign/malignant and 2 cases of discordance mesenchymal/non mesenchymal. Minor histological discrepancies - not affecting the management of the patient - were observed in 18 cases (20.4%). A major discordance in grading - potentially changing the management of the patient - was noted in 7 cases (7.9%), and a minor discrepancy in 5 cases (5.7%).

DISCUSSIONS: Some histological types were clearly overdiagnosed, like "adult fibrosarcomas" and "malignant peripheral nerve sheet tumors" (MPNST), mostly converted after the audit into "undifferentiated spindle cell sarcomas" or other types of sarcomas. Some "unclassified" sarcomas and "undifferentiated pleomorphic sarcomas" could be re-classified with the aid of an extensive panel of antibodies. Overall, immunohistochemistry was responsible, but not in exclusivity, for half of the minor discrepancies, and for 2 out of 3 cases of major histological discrepancies. Otherwise, the main cause of discrepancies was the difficulties in the interpretation of the morphology. Molecular biology was decisive in one case. Most grading discrepancies resulted from the appreciation of the mitotic index.

CONCLUSIONS: The profile of the sarcomatous pathology in the northwest region of Romania does not appear to differ significantly from other parts of Europe or the world, but a prospective epidemiological study would be necessary to confirm this assessment. The expansion of immunohistochemical antibody panel, the over-specialization of pathologists and, in the future, the establishment of a national network of referral centers in sarcoma pathology, are required for a high level of histological diagnosis in Eastern Europe. A periodic external audit, continuing this trans-European collaboration between the two centers, would be beneficial for monitoring progress.