Sarcoma pleomórfico indiferenciado de alto grado como tumor primario de mama en una paciente de 12 años: reporte de caso

High-grade undifferentiated pleomorphic sarcoma (UPS) of the breast is an extremely rare entity in children, representing less than 1% of malignant breast tumors. It poses a challenge in diagnosis and treatment due to the lack of specific guidelines. We describe the case of a 12-year-old patient with no significant medical history who presented to a tertiary care hospital with a rapidly growing, painful breast mass with cutaneous changes. Imaging studies showed a complex BIRADS 4C mass with no sign of metastasis. The case was submitted to a multidisciplinary board, which indicated primary surgical management. The postoperative pathology report indicated UPS. Adjuvant intensity-modulated radiation therapy (IMRT) and chemotherapy with ifosfamide and doxorubicin were indicated according to the protocol for pediatric non-rhabdomyosarcoma. The patient showed a favorable postoperative outcome, with complete graft healing and no signs of relapse to date. This case highlights the importance of aggressive surgical management and personalized adjuvant treatment in pediatric breast sarcomas, emphasizing the need for additional studies to establish specific management guidelines and optimize outcomes in this population.