DISCORDANCE BETWEEN THE INITIAL DIAGNOSIS OF SARCOMAS AND SUBSEQUENT HISTOPATHOLOGICAL REVISION AND MOLECULAR ANALYSES IN A REFERENCE ONCOLOGY CENTER IN BRAZIL

Introduction: Sarcomas correspond to a group of rare and heterogeneous tumors of mesenchymal origin. The accurate diagnosis of sarcomas represents a major challenge due to the diversity of demographic, phenotypic/pathologic, and molecular aspects. These hurdles are further enhanced in developing countries due to the limited availability of specialized pathology centers, multidisciplinary teams, and diagnostic tools, which may directly affect the treatment plan. Objective: To characterize the impact of diagnostic review by reference pathologists in a reference center in Brazil. Methods: We retrospectively reviewed sarcoma biopsies which were initially evaluated at outside laboratories and were subsequently analyzed by two dedicated pathologists between 01/2014 and 12/2020. Based on the Ray-Coquard et al. criteria, and following extraction of demographic and tumor characteristics, revised results were classified onto complete discordance (CD) (benign versus malignant, sarcoma versus other malignancy), partial concordance (PC) (similar diagnosis of connective tumor, but different grade/histological subtype/ differentiation), and complete concordance (CC) (both results presented with the same conclusion). Results: A total of 197 patients (pts) were included, with a median age at diagnosis of 47.1 years; 57.9% were male, and 86.8% presented with localized disease. The most common primary sites were lower extremities (34.6%), retroperitoneum (11.3%), and trunk (9.3%). Following the revision, the most frequent subtypes were undifferentiated pleomorphic sarcoma (20.3%), liposarcomas (13.1%), and leiomyosarcoma (6.6%). CC between diagnosis was observed in 82(41.6%), PC in 89(45.2%), and CD in 26 (13.2%) of the cases, leading to a total proportion of non-concordance of 58.4%. Molecular analyses were performed in 44(22.3%) cases (NGS panels:79.5%; FISH:20.5%), with findings of diagnostic relevance in 31.8% of those. Conclusion: In nearly 60% of the cases, the initial diagnosis was at least partially modified when revised in a reference center, a discordance that may translate into the design of an inappropriate therapeutic strategy. This highlights the importance of the management of sarcoma pts in reference centers and justifies the assembly of referral networks in countries with limited healthcare resources.