Artefactual Epithelial Displacement in a Papilloma with Extensive Usual Duct Hyperplasia Mimics a Solid Papillary Carcinoma with Invasive Growth.

Mammary solid papillary carcinoma and usual duct hyperplasia (UDH) of the breast are morphological look-alikes, characterized by cellular streaming, solid growth, and a lack of high-grade nuclear atypia. Here, we report a challenging papillary lesion in the breast of a 48-year-old woman that presented with a double pitfall. A core needle biopsy showed a solid papillary proliferation of epithelial cells with oval to round overlapping nuclei, surrounded by a sclerotic stroma.