Extensive Squamosu Metaplasia Mimicking Squamous Cell Carcinoma in Fibroadenoma

ABSTRACT

We report a fibroadenoma with extensive squamous metaplasia in the breast. A 21-year-old woman presented with a mass of the left breast. Breast ultrasonography showed a 1.8x1.7 cm sized, well-circumscribed mass in left subareolar region. The mass was excised. Grossly, the mass was well circumscribed and the cut surfaces were grayish-white in color and elastic in consistency. Microscopically, the breast lesion showed the histological features of fibroadenoma. There were areas of extensive squamous metaplasia seen as isolated clusters or involving duct. But some metaplastic clusters surrounded by fibrous stroma were compressed and distorted and separation of cells into isolated clusters mimicked invasive carcinoma. Co-expression of CK 5/6, high molecular weight CK and p63 in areas of squamous metaplasia and normal myoepithelial cells supported myoepithelial cell origin of metaplastic cells.