Circulating tumor cells are breakaway tumor cells that can seed secondary tumors (metastases) and are commonly detected in the blood of patients with cancer. Dual-positive cells are circulating cells that bear both tumor-cell and immune-cell markers and are thought to be hybrid cells resulting from rare fusions of tumor cells with immune cells. Recent studies have linked DP cells’ presence in patients’ blood to worse outcomes in melanoma and pancreatic cancer.

In the new study, the researchers linked DP cells to shorter survival times in patients with advanced breast cancer, especially the aggressive triple-negative breast cancer subtype. The team also showed with animal models that DP cells can seed breast cancer metastases.