How can squamous cancer get in your blood and is it fatal?

All cancers: develop a vascular supply in order to grow. Tumor cells are "shed" into the blood vessels or lymphatics, from which they can potentially seed distant parts of the body. With metastases, prognosis is worse but not necessarily fatal. The propensity for metastasis and the prognosis depends on the type of tumor and various characteristics such as size or location.