HER2-Positive Pleomorphic Lobular Breast Cancer in a 43-Year-Old Woman

What happened, in summary

A 43-year-old woman sought care in November 2024 after noticing a painless lump in her right breast for about 4 months. Examination found a firm mass, and imaging showed several suspicious areas across the right breast. The largest lesion on MRI measured about 2 cm, and an enlarged right axillary lymph node was also seen. She underwent a modified radical mastectomy with lymph node surgery the next day.

Pathology found multifocal invasive pleomorphic lobular carcinoma, an uncommon form of lobular breast cancer. Cancer was found in 3 lymph nodes: 1 of 2 sentinel nodes and 2 of 13 additional axillary nodes. The tumor was HER2-positive and negative for both estrogen and progesterone receptors. The pathology also showed lymphovascular and nerve involvement, while the surgical margins were clear.

After surgery, she received 6 cycles of paclitaxel and carboplatin together with the HER2-targeted medicines trastuzumab and pertuzumab. She then completed 25 radiation treatments. Trastuzumab and pertuzumab were continued as adjuvant treatment, and neratinib was later added. She experienced mild nausea and vomiting after chemotherapy, which resolved with supportive medication. Her treatment therefore combined surgery, chemotherapy, radiation, and extended HER2-directed therapy for a node-positive, HER2-positive breast cancer.