Coexistence of Pseudoangiomatous Stromal Hyperplasia and Benign Phyllodes Tumor: A Rare Histopathological Challenge

Phyllodes tumors are uncommon fibroepithelial breast neoplasms with potential for local recurrence and, rarely, malignant transformation. Pseudoangiomatous stromal hyperplasia (PASH) is a benign proliferative lesion of the breast stroma, usually encountered as an incidental microscopic finding but occasionally presenting as a mass-forming lesion. The coexistence of PASH within a phyllodes tumor is rare and can pose diagnostic challenges on core biopsy. We report the case of a 48-year-old multiparous woman who presented with a gradually enlarging left breast lump over two years. Clinical examination and imaging favored a phyllodes tumor. Fine-needle aspiration cytology (FNAC) and core biopsy, however, showed PASH-like features. Wide local excision was performed, and histopathology confirmed a benign phyllodes tumor with extensive PASH. The postoperative course was uneventful, and the patient remained asymptomatic at six months of follow-up. The presence of PASH-like features on core biopsy created a diagnostic dilemma, as the low stromal cellularity and pattern mimicked benign proliferative lesions, leading to an underestimation of the underlying fibroepithelial neoplasm. This underscores the importance of clinicoradiologic-pathologic correlation and surgical excision for definitive diagnosis in such cases.