What happened, in summary

A 53-year-old woman was diagnosed with neuroendocrine breast cancer, a rare breast cancer subtype. She had no family history of breast cancer. Her tumor measured 3.0 cm and was grade 3. Sentinel lymph-node biopsy examined 6 nodes, and none contained cancer.

The tumor strongly expressed chromogranin and synaptophysin, supporting the neuroendocrine diagnosis. It was hormone receptor-positive and HER2-negative, with an estrogen receptor score of 285 and progesterone receptor score of 300. Ki-67 was 40%, suggesting active cell growth and creating concern despite the negative lymph nodes.

Her team used the Oncotype DX multigene test to clarify whether chemotherapy was likely to add benefit. Her Recurrence Score was 13. This was much lower than the scores of the other 3 patients in the case series and below the threshold of 25 used for chemotherapy decisions.

The low score suggested little or no expected chemotherapy benefit and supported avoiding unnecessary chemotherapy despite the grade 3 appearance and high Ki-67. Her case showed why tumor biology could point in a different direction from standard pathology features. Her low genomic score gave the team evidence to consider sparing her chemotherapy.