Pancreatic metastasis from a malignant phyllodes tumor of the breast: a case report.

Herein, we report a rare case of pancreatic metastasis originating from a malignant phyllodes tumor of the breast. A 45-year-old woman initially underwent a partial mastectomy for malignant phyllodes tumor of the left breast, followed by a total mastectomy for local recurrence. Six years later, the patient presented with abdominal pain. Computed tomography revealed a heterogeneous mass with cystic degeneration in the pancreatic tail, morphologically resembling the previously resected breast lesions. Based on the patient's history and imaging findings, pancreatic metastasis from malignant phyllodes tumor was suspected. Endoscopic ultrasound-guided fine-needle aspiration of the solid component was performed, and histopathological examination revealed a sheet-like proliferation of atypical cells with spindle-shaped enlarged nuclei within an eosinophilic stroma. Immunohistochemical staining for AE1/3 cytokeratin was negative, consistent with metastatic malignant phyllodes tumor. The patient declined further treatment and died approximately two months after diagnosis.