Mammary epidermoid inclusion cysts after wide-core needle biopsies

Aims: To investigate the prevalence of squamous epidermoid inclusion cysts after wide‐core needle biopsy. Methods and results: Epidermoid inclusion cysts were found in five of 17 surgical excisions (29%) after preliminary wide‐core needle biopsies in a 7‐month period. Thereafter they were not seen in 26 subsequent postwide‐core surgical excisions in a period of 6 months. Conclusions: The cysts appear to be an iatrogenic complication of wide‐core biopsy, and need morphological recognition in order to avoid confusion with spontaneous squamous metaplasia of benign or malignant breast epithelium. Longer term implications are unknown.