Here within the bladder’s microenvironment, we can see clusters of thin, delicate, stalk-like projections extending outward from the bladder wall.
These structures, known as non-invasive papillary carcinomas, remain superficial, anchored to the transitional epithelium (urothelium) — a fragile layer that acts as a barrier between the bladder’s interior and surrounding tissues – and where most bladder cancers begin.
Our journey continues past these small papillary structures until we encounter a larger, more irregular mass. The presence of such a irregular structure raises suspicion that it may have breached the urothelium, signaling a possible shift to an invasive stage of cancer. At this point, the tumor likely extends deeper into the bladder wall, a critical progression that significantly increases the risk of spread to surrounding tissues.

Source: hybridmedicalanimation and world_of_biology_wob