Metastatic Neuroendocrine Breast Cancer With Severe Hormone Overproduction

What happened, in summary

A 39-year-old woman presented with a rapidly enlarging right breast mass. Biopsy showed a poorly differentiated breast carcinoma with high-grade neuroendocrine features. Testing showed ER negativity, focal PR positivity, and HER2 negativity. Initial imaging was negative, but a PET scan 2 weeks later revealed widespread liver and bone metastases, making this Stage IV disease.

She began first-line treatment with cisplatin, etoposide, and durvalumab. After 4 cycles, both the breast tumor and metastatic disease had progressed. She underwent an urgent right simple mastectomy for local control. Final pathology confirmed high-grade neuroendocrine carcinoma of the breast. A PIK3CA mutation was later identified. Second-line doxorubicin and cyclophosphamide was followed by nab-paclitaxel after further progression in the liver, bones, and lymph nodes.

During this period she developed severe hormone overproduction caused by the cancer, leading to very low potassium and Cushing syndrome. Medical treatment was not sufficient, so she underwent bilateral adrenalectomy, which improved her symptoms and quality of life temporarily. Alpelisib was being pursued for the PIK3CA mutation but was not available in time. About a month after discharge she was readmitted, deteriorated rapidly, developed cardiac arrest, and died during progressive metastatic disease.