Digital Atlas of Breast Pathology by Meenakshi Singh, MD © - Department of Pathology, Stony Brook University Medical Center

Pseudoinvasion of capsule of an encysted papilloma.
Most papillary carcinomas are surrounded by a zone of fibrosis with chronic inflammation and recent or resolved hemorrhage. Clusters of epithelial cells within this area can be difficult to interpret. The most reliable evidence of invasion is extension of carcinoma beyond the border of the tumor and an adjacent stroma reaction.