Complex Fibroadenoma with Pronounced Squamous Metaplasia: A Rare Case Report, Differential Diagnostic Considerations, and Associated Breast Cancer Risk.

Squamous metaplasia of the breast is a rare and unusual finding. A number of benign and malignant differential entities exist when squamous cells are present in a breast lesion. Our patient was found to have pronounced squamous metaplasia and keratin cysts arising in a complex fibroadenoma. The rare nature of squamous metaplasia arising in such a lesion poses some diagnostic challenges, as squamous epithelium and squamous metaplasia in the breast may raise suspicion for malignancy. Herein we present a unique case and discussion of benign and malignant differential entities. We also retrospectively reviewed a series of complex fibroadenomas in our institution, including the demographic and histologic features, and more importantly the associated breast cancer risk.