Characterization of ultrarare sarcomas in a high-volume referral center in Latin America

<h2>Abstract</h2><h3>Background</h3> Ultrarare sarcomas are a diverse group of malignancies with an incidence of less than 1% of all sarcomas. Due to their rarity, knowledge about their biology and treatment is limited. Most data come from high-income countries, with little representation from Latin America. This study characterizes ultrarare sarcomas' clinical and pathological features in a Latin American referral center. <h3>Methods</h3> A retrospective cohort study was conducted at a high-volume sarcoma center, including patients diagnosed between 2000 and 2020. Histopathological diagnoses were defined by expert pathologists. Demographic, clinical, and treatment data were collected. Statistical analyses included descriptive statistics and Kaplan-Meier survival analysis. <h3>Results</h3> We included 148 patients (median age: 42 years, 54.7% female). The most common histological subtypes were epithelioid sarcoma (19.6%), myxo-inflammatory fibroblastic sarcoma (12.8%), and alveolar soft part sarcoma (9.5%). Most tumors (77.7%) were high-grade, and 22.3% had metastases at diagnosis. Surgery was performed in 77.7% of cases, achieving R0 resection in 51.4%. Adjuvant radiotherapy was used in 39.9%, and chemotherapy in 26.4%. Overall survival was 48.2 months. Metastatic disease, high-grade tumors, and positive margins were associated with worse survival (p<0.001). <h3>Conclusion</h3> This study highlights the heterogeneity of ultrarare sarcomas and the importance of multidisciplinary management in Latin America. Further research and collaboration are needed to improve outcomes.