Benign Phyllodes Tumor With Cystic Squamous Metaplasia: A Cytohistological Correlation of a Rare Case

BACKGROUND: Phyllodes tumors (PTs) are uncommon biphasic fibroepithelial neoplasms of the breast occurring in elderly females with a peak incidence between 45 and 49 years. Depending on various histological criteria, they are subdivided into benign, borderline, and malignant forms. Metaplastic changes occur, but are quite infrequent and cystic squamous metaplasia is very rare among the observed metaplastic changes in PT. CASE: The current paper presents the case of a 41-year-old female with a progressively enlarging swelling in the left breast. Subsequent histopathological examination revealed benign PT with cystic squamous metaplasia. The previously done fine needle aspiration smears were also reviewed, which showed important diagnostic clues to this rare entity, but were ignored due to the rarity of the lesion. CONCLUSION: The case was presented because of its unique cytological and histopathological morphology and also to determine the role of aspiration cytology to diagnose such a rare occurrence.