HER2-Positive Acantholytic Squamous Breast Cancer Responds Completely to Preoperative Therapy

What happened, in summary

A woman in her late 50s developed a large right-breast mass with skin swelling and ulceration. Testing showed a rare acantholytic squamous cell carcinoma of the breast that was HER2-positive. The tumor was described as locally advanced, with no distant metastases identified.

She received 6 cycles of albumin-bound paclitaxel, carboplatin and trastuzumab before surgery. The breast mass shrank substantially. She then underwent right mastectomy with axillary lymph-node dissection, and none of the 37 removed lymph nodes contained cancer. The invasive component had achieved a pathologic complete response, although a small amount of carcinoma in situ remained.

She continued trastuzumab for 17 cycles and started anastrozole because the residual in-situ component expressed estrogen and progesterone receptors. Chest-wall and supraclavicular radiotherapy were not given. During 1.5 years of follow-up with examinations every 3 months, there was no recurrence or metastatic disease. The case documents a strong response to HER2-directed preoperative treatment in this uncommon breast-cancer subtype.