Trastuzumab not for ductal carcinoma in situ?

Ductal carcinoma in situ (DCIS) is a preinvasive breast lesion accounting for approximately 30% of all newly detected breast cancers in the US. DCIS has been separated into two groups by architecture (comedo versus noncomedo) and nuclear grade. The expression of biological markers in DCIS, however, would reflect the true biologic potential of the lesion. Patients with estrogen receptor (ER)-negative, human epidermal growth factor-2 (HER-2)-positive DCIS pose a treatment challenge. They are not candidates for tamoxifen; trastuzumab has an undetermined role in DCIS. In this report, we present a case of a 45-year-old woman diagnosed with invasive breast cancer and ER-negative/HER-2-positive DCIS who developed recurrence and progression of DCIS as manifested by a new palpable mass while receiving trastuzumab as part of adjuvant treatment for invasive breast cancer. The potential clinical implications are discussed.