Anonymized, coded images of the cases

Soft tissue sarcomas are rare neoplasms, accounting for approximately 1% of all malignancies and comprising more than 50 histological subtypes. Their diagnosis is complicated by overlapping morphology, evolving classifications, and reliance on ancillary techniques, particularly in tumors with spindle cell features. We retrospectively analyzed 90 spindle cell sarcomas referred for second opinion. Initial morphology-based diagnoses were reassessed alongside clinical data, with additional immunohistochemical and molecular studies performed when indicated. Diagnostic discordance was identified in 61% of cases. Final diagnoses were predominantly established through expert morphological evaluation supported by targeted immunohistochemistry, while selective molecular analyses were instrumental in confirming or excluding specific entities. Discrepancies were mainly related to overlapping spindle cell morphology, incomplete clinical information, and limited ancillary testing at initial assessment. Our findings highlight that expert second-opinion review and the integrated use of morphology, immunohistochemistry, and selective molecular testing substantially improve diagnostic accuracy, with significant implications for treatment decisions and prognostic evaluation.