Spectrum of atypical ductal hyperplasia (ADH) and ductal carcinoma in-situ (DCIS): Diagnostic challenges

Breast specimens are some of the more common specimens sent to the pathology laboratory for diagnosis. From a clinical perspective, the diagnoses fall into three broad categories: benign, atypical and malignant with patients then being managed according to established guidelines. However, the pathologic diagnosis can sometimes be challenging, and the distinction between these categories is sometimes far more subtle and subjective than non-pathologist may understand. One recurring diagnostic challenge in breast pathology is the diagnosis of atypical ductal hyperplasia (ADH) versus ductal carcinoma in situ (DCIS). While many cases are straightforward, others are quite borderline and challenging to classify consistently with significant interobserver variation amongst pathologists. The distinction between ADH and DCIS is critical from a clinical management perspective because one is treated as a risk factor, and the other as a malignancy that will be completely surgically excised and may require radiation therapy. This review will address the spectrum of ADH and DCIS with the associated diagnostic challenges in the real-world setting from presentation at core needle biopsy to surgery.