CONFRONTING THE UNCOMMON: A CASE REPORT ON MALIGNANT PHYLLODES TUMOUR OF THE BREAST INITIALLY MISDIAGNOSED AS INVASIVE DUCTAL CARCINOMA

Abstract

Background:

Phyllodes tumours (PTs) are rare fibroepithelial neoplasms of the breast, constituting 0.3–1% of all breast tumours. Malignant PTs comprise only 10–20% of cases and are prone to rapid growth, local recurrence, and distant metastasis. Differentiation from invasive ductal carcinoma (IDC) can be challenging, especially with core needle biopsy due to sampling limitations.

Case Presentation:

We report a 47-year-old female who presented with a 10×7 cm lump in the right breast for 4 months. Initial core needle biopsy suggested IDC, triple-negative subtype, with Ki-67 of 10%. PET-CT revealed a hypermetabolic breast mass (T2N0M0). She underwent right modified radical mastectomy. Histopathology demonstrated stromal atypia, marked nuclear pleomorphism, high mitotic activity (20–30/10 HPF), and CD34 focal positivity in malignant spindle cells, consistent with malignant PT. Postoperatively, she received 25 fractions of adjuvant radiotherapy. She is on a close follow-up schedule with no recurrence at present.

Conclusion:

This case highlights the diagnostic pitfalls in differentiating malignant PT from IDC on core needle biopsy, the necessity of extensive tissue sampling, and the role of histopathology in guiding definitive management.