What happened, in summary

A 69-year-old woman was diagnosed in 2009 after a screening mammogram found a 1 cm suspicious lesion in the left breast. Surgery revealed a much larger invasive ductal carcinoma measuring more than 5 cm with prominent lobular features. Fourteen of 18 axillary lymph nodes contained metastatic carcinoma, making the initial disease Stage III.

The tumour was strongly estrogen-receptor positive at more than 80%, progesterone-receptor positive in 50–60% of cells and HER2 negative. She received radiation to the left breast and regional lymph nodes and completed 6 cycles of fluorouracil, epirubicin, cyclophosphamide and docetaxel. Endocrine therapy followed with letrozole, later changed to exemestane in 2012.

A screening colonoscopy in 2011 found a rectosigmoid polyp. Biopsy unexpectedly showed metastatic breast adenocarcinoma rather than a new colorectal primary. Repeat biopsies 15 and 31 months later again showed breast-cancer metastases in the transverse colon, sigmoid and rectum. The metastatic tissue remained estrogen-receptor positive and HER2 negative but had lost progesterone-receptor expression.

Laparoscopy later showed carcinomatosis involving the peritoneum, diaphragm, liver and bowel. Biopsies from the pelvic wall, adnexa and appendix also confirmed metastatic breast cancer. The later findings establish progression to Stage IV disease.