Concurrent malignant phyllodes tumor and invasive ductal carcinoma in a young female: a rare case report.

Introduction: Phyllodes tumors are rare fibroepithelial breast neoplasms, typically affecting middle-aged women. Malignant phyllodes tumors (MPTs) account for a minority of these cases and are extremely uncommon in adolescents. The synchronous presentation of MPT with contralateral invasive ductal carcinoma (IDC) is exceptionally rare and presents unique diagnostic and therapeutic challenges. Case presentation: We report the case of a 19-year-old female who presented with a rapidly enlarging mass in the left breast, initially misdiagnosed as an abscess. On physical examination, a distinct right breast mass and bilateral axillary lymphadenopathy were also noted. Imaging and biopsy revealed an MPT in the left breast. Histopathology confirmed IDC in the right breast and metastatic adenocarcinoma in both axillae. Immunohistochemistry revealed high proliferative activity in the IDC. The patient underwent left mastectomy and was started on systemic chemotherapy, with a favorable initial response. Clinical discussion: This case underscores the importance of considering rare malignancies in adolescents with atypical breast presentations and highlights the diagnostic limitations of imaging alone. The concurrent diagnosis of two distinct breast cancers in a young patient raises concern for a possible underlying genetic predisposition and supports the need for a multidisciplinary approach to management. Conclusion: The simultaneous occurrence of MPT and IDC in adolescents is extraordinarily rare. Early histopathological assessment, comprehensive bilateral evaluation, and coordinated oncologic care are essential for optimal management in such complex cases.