MammaPrint classifies patients as either high risk or low risk of recurrence over a 10-year period while BluePrint classifies patients by breast cancer subtype.
Researchers developing the gene expression-based test say it could bring objectivity to a subjective diagnosis and result in more targeted treatments.
The company will offer 4 million shares of common stock at a price of $12.50 per share, with an option for underwriters to purchase up to an additional 600,000 shares.
NanoString Technologies hopes to use proceeds from the stock offering to support the commercial launch of its Digital Spatial Profiling platform next year.
The two companies are entering a partnership to introduce diagnostic tests using NanoString's nCounter technology in Japan, beginning with a lymphoma assay.