BEYOND THE LEAF‑LIKE PATTERN: MALIGNANT PHYLLODES TUMORS WITH HETEROLOGOUS DIFFERENTIATION: A CASE SERIES

Background: Malignant Phyllodes Tumors (MPTs) are rare fibroepithelial breast neoplasms, accounting for 8–20% of all Phyllodes tumors. When heterologous differentiation—such as liposarcoma, fibrosarcoma, osteosarcoma, chondrosarcoma, angiosarcoma, or rhabdomyosarcoma —is present, these neoplasms exhibit unique histopathology and clinical characteristics, though available data on this phenomenon remains limited due to its rarity. Case presentation: Three female patients aged 48 to 64 presented with progressively enlarging, painless breast lumps ranging from 4.8 to 6.4 cm. Tumors were located in different breast quadrants. Histopathological examination confirmed malignant Phyllodes tumors with rare heterologous sarcomatous differentiation—chondrosarcoma in Case 1, angiosarcoma in Case 2, and combined osteosarcoma with chondrosarcoma in Case 3. All underwent modified radical mastectomy; and axillary lymph node dissection (ALND) was performed in one case. No recurrence was noted in Cases 1 and 2 at 18 and 6 months, respectively. No adjuvant therapy was given. Discussion: MPTs with heterologous sarcomatous elements remain an exceptionally rare subgroup, posing significant diagnostic ambiguity. Thorough histologic sampling and immunohistochemistry are essential to differentiate these from metaplastic carcinoma or primary breast sarcomas. Prognostic indicators and treatment protocols for these variants are not well established due to their rarity. Current practice supports wide surgical excision with negative margins; adjuvant therapy decisions should be individualized, and close surveillance is advisable given the potential for aggressive behavior. Conclusion: The case series highlight the exceptionally rare presentation of malignant Phyllodes tumours with heterologous sarcomatous differentiation. Detailed case documentation and long-term follow-up are essential to better characterize their clinical trajectory and inform optimal management strategies.