What happened, in summary

A 75-year-old woman found a lump in her right breast during a self-examination. An initial biopsy was read as invasive ductal carcinoma, but repeat testing at a specialist center showed a rare primary small cell neuroendocrine carcinoma of the breast. The tumor was positive for neuroendocrine markers and estrogen receptor, negative for HER2 and had a very high Ki-67 of 95%. Initial CT, MRI and bone scans found no distant spread.

In January 2022, she underwent a right simple mastectomy with sentinel lymph-node biopsy. The tumor measured 4.6 cm, was grade 3 and showed lymphovascular invasion. One of 2 sentinel nodes contained a 1.2 mm micrometastasis, giving a pathologic classification of pT2 pN1mi(sn). The margins were clear, and a small area of high-grade ductal carcinoma in situ was also present. She then received 4 cycles of carboplatin and etoposide between March and May 2022, followed by CT and MRI surveillance every 4 months.

A 0.6 cm liver lesion appeared in March 2023 and grew to 2.5 cm by July. After PET imaging confirmed concern for metastasis, surgeons removed liver segments 7 and 8 along with the gallbladder. Pathology confirmed a 4 cm breast neuroendocrine cancer metastasis. She completed 4 more dose-reduced cycles of carboplatin and etoposide by March 2024.

Multiple liver lesions returned later in 2024. Another dose-reduced chemotherapy course produced an initial response, but by May 2025 new liver lesions and abdominal lymph-node involvement were present. The tumor board planned capecitabine and temozolomide as the next treatment.