Diagnostic Consideration of Spindle Cell Proliferations in the Breast

Cutaneous presentation of a distant metastasis of malignant phyllodes tumor

“…Phyllodes tumors are part of a broader differential diagnosis of spindle‐cell proliferations in the breast, which includes non‐neoplastic [pseudoangiomatous stromal hyperplasia (PASH), nodular fasciitis, reactive spindle‐cell nodule], benign neoplastic (fibromatosis, myofibroblastoma), and malignant [metaplastic (spindle‐cell) carcinoma, primary mammary sarcoma] stromal tumors 6 . Primary breast sarcomas comprise a small fraction of a percentage of breast tumors, calculated at <1.0%, 7,8 and as such are extremely rare.…”