Again...the anatomy of the bladder....
The bladder itself is made up of four layers. These layers are important landmarks in determining how deeply the tumor has invaded and the ultimate stage of the cancer.
Epithelium: The epithelium, which lines the bladder and is in contact with the urine, is referred as transitional epithelium or urothelium. Most bladder cancers originate from the cells of this transitional epithelium. The urethra, ureters and the pelvis of the kidney are also lined by this transitional epithelium, therefore, the same types of cancers seen in the bladder can also occur in these sites.
Lamina propria: Under the epithelium is the lamina propria, a layer of connective tissue and blood vessels. Within the lamina propria, there is a thin and often discontinuous layer of smooth muscle called the muscularis mucosae. This superficial layer of smooth muscle is not to be confused with the true muscular layer of the bladder called the muscularis propria or detrusor muscle.
Muscularis propria or detrusor muscle: This deep muscle layer consists of thick smooth muscle bundles that form the wall of the bladder. For purposes of staging bladder cancer, the muscularis propria has been divided into a superficial (inner) half and a deep (outer) half.
Perivesical soft tissue: This outermost layer consists of fat, fibrous tissue and blood vessels. When the tumor reaches this layer, it is considered out of the bladder.
In the Biopsy to determine stage/grade/type of bladder cancer "Muscle Bundles" are removed/or looked at, to determine if the cancer is Muscle Invasive. This helps with the proper staging/grading. Another reason to have a top notch surgeon/hospital/pathology lab as all of this is subjective, and you want the best eyes looking at them. I may have over simplified the definition. In layman's terms of course.
Caregiver for my Wonderful Husband Angelo, who has Metastatic Bladder Cancer.
Life isn't about how to survive the storm, but how to dance in the rain.