Discordance Between the Initial Diagnosis of Sarcomas and Subsequent Histopathological Revision and Molecular Analyses in a Sarcoma Reference Center in Brazil.

Purpose: To investigate the discordance in sarcoma diagnoses between nonspecialized institutions following revision by dedicated sarcoma pathologists at a reference center in Brazil and the relevance of molecular pathology in this context.

Methods: We conducted a retrospective analysis of sarcoma samples initially analyzed at outside laboratories and subsequently reviewed by two specialized pathologists between January 2014 and December 2020. After obtaining demographic and tumor characteristics, pathology results were matched and classified as complete discordance (CD; benign malignant, sarcoma other malignancies), partial concordance (similar diagnosis of connective tumor, but different grade/histological subtype/differentiation), and complete concordance (CC). The concordance for histology or grade, and the role of molecular assessments supporting the diagnosis were also independently determined. Statistical analyses were conducted through the kappa coefficient of agreement and adherence by χ test, χ test by Person, and Fisher exact test.

Results: In total, 197 cases were included, with samples obtained predominately from male patients (57.9%) and localized/primary tumors (86.8%). Following revision, the most frequent final diagnoses were undifferentiated pleomorphic sarcoma (17.8%), well-differentiated/dedifferentiated liposarcoma (8.6%), and leiomyosarcoma (7.6%). CD was found in 13.2%, partial discordance in 45.2%, and CC in 41.6% of reviews ( < .001). We found a concordance for histology or grade of 53.5% ( < .001) and 51.8% ( < .001), respectively. Molecular assessments, comprising next-generation sequencing panels (79.5%) and fluorescent in situ hybridization (20.5%), were performed in 44 (22.3%) cases, with findings classified as of diagnostic relevance in 31.8%.

Conclusion: In nearly 60% of the cases, the initial sarcoma diagnosis was modified when revised by a reference center and dedicated pathologists, assisted by molecular pathology techniques. These results justify the assembly of referral networks in countries with limited health care resources.