Phyllodes tumor with osteosarcomatous differentiation: a comparative immunohistochemical study between epithelial and mesenchymal cells

Abstract

Aims and background: Phyllodes tumor of the breast with osteosarcomatous differentiation is rare and very little is known about its molecular profile.

Methods and study design: An immunohistochemical panel with 37 primary antibodies including cytokeratins, mesenchymal markers, key regulators of the cell cycle, oncogenes, apoptosis-related proteins, metalloproteinases and their inhibitors was performed on a formalin-fixed paraffin-embedded sample of phyllodes tumor with osteosarcomatous differentiation in a 49-year-old woman.

Results: Antiapoptotic stimuli (survivin) predominated in sarcomatous cells. Antiproteolytic stimuli (TIMP-1, TIMP-2 and PAI) were preponderant in all cells, a surprising fact in view of the aggressiveness of the neoplasm. The immunoprofile of the osteoblastic and stromal cells was quite similar, except for c-erbB-3, c-myc, cyclin D1 and p21. Both exhibited positive cells for actin, MyoD1 and GFAP.

Conclusions: Our results suggest that this osteosarcoma may have originated from metaplasia of stromal cells that underwent a malignant change.