A case of HER-2-positive advanced inflammatory breast cancer with invasive micropapillary component showing a clinically complete response to concurrent trastuzumab and paclitaxel treatment

We report a case of HER-2-positive advanced inflammatory breast cancer with invasive micropapillary component showing a complete response to trastuzumab and paclitaxel treatment. A 37-year-old woman was referred to our hospital for right breast swelling with broad skin redness and right axillary tumor. Ipsilateral infraclavicular and contralateral axillary lymph nodes swelling were also recognized. The histopathological findings of core-needle biopsy specimens from primary breast tumor and ipsilateral axillary lymph node were invasive ductal carcinoma with a micropapillary component. Immunohistochemical examination gave a negative result for estrogen receptor (ER)/progesterone receptor (PgR), and overexpression of HER-2 (Hercep Test 3+). Advanced inflammatory breast cancer with an invasive micropapillary component was diagnosed (T4d N3 M1 (LYM), stage IV). The patient was treated with combination chemotherapy using weekly paclitaxel and trastuzumab. After administration of three courses, the breast swelling, skin redness, and lymph node swelling disappeared completely. She maintained complete remission of disease for 12 months and was judged to have a clinically complete response by the RECIST criteria. Invasive micropapillary carcinoma is known to be an aggressive histological type associated with a high incidence of lymph node metastasis and poor prognosis. This is the first reported case of advanced inflammatory breast cancer with an invasive micropapillary component showing a clinically complete response to trastuzumab-containing treatment. This report suggests trastuzumab-containing chemotherapy is a promising therapy for HER-2-positive advanced invasive micropapillary carcinoma.