Similar to bladder cancers, UTUCs can develop as low- or high-grade tumors.  In general, low-grade tumors are not invasive and very rarely spread from the kidney or ureter.  However, they often recur and management involves treating visible tumors and trying to preserve the urinary tract – as these tumors are more likely to recur in the urinary system than they are to spread.  High-grade tumors have an aggressive appearance under a microscope and are assumed invasive in the kidney or ureter.  In the bladder, a thick bladder muscle (called the detrusor) acts as a barrier to confine invasive cancers but in the kidney and ureter, this muscle does not exist.  High-grade UTUC has the potential to spread from the kidney or ureter and is most often treated with surgical removal of the kidney and ureter – an operation called radical nephrouretectomy.  High-grade UTUC can be aggressive and an expert may recommend systemic therapy (for example, chemotherapy) before or after surgery to reduce the risk of recurrence elsewhere in the body.    An expert pathologist is often enlisted to determine low- and high-grade urothelial cancers, as this distinction can dramatically impact management choices.