Challenging Biopsy of a Benign Breast Lesion With Malignancy Features: Cystic Apocrine Metaplasia

Apocrine metaplasia is a benign epithelial change that primarily occurs in the terminal lobule, where the normal cuboidal epithelium is replaced by secretory apocrine cells with abundant eosinophilic cytoplasm. Even with the most recent advances in imaging modalities, radiographic findings can sometimes be equivocal in the characterization of breast lesions, leading to the necessity of tissue sampling. We report a challenging case of biopsy-proven cystic apocrine metaplasia that presented in the posterior depth with initially suspicious imaging findings concerning for malignancy. Understanding the histological basis of apocrine metaplasia and correlating it with recognized imaging features may increase diagnostic accuracy and reduce tissue resampling due to discordant histopathological results.