by Jason Wasserman MD PhD FRCPC
July 12, 2022
Low grade papillary urothelial carcinoma is a type of cancer that starts in a part of the body called the urinary tract. The urinary tract includes the bladder, ureters, urethra, and kidneys. Most tumours are found in the bladder. This type of cancer is described as “low grade” because the tumour cells look very similar to the normal urothelial cells found in the urinary tract.
Low grade papillary urothelial carcinoma starts from specialized urothelial cells that cover the inside surface of the urinary tract and create a barrier called the urothelium. Below the urothelium is a thin layer of tissue called the lamina propria. This type of cancer is described as non-invasive because the tumour cells are only found in the urothelium. Some pathology reports may also say that “no invasion” of the lamina propria was seen to emphasize the non-invasive nature of the tumour.
The diagnosis is usually made by looking at a urine sample under a microscope. The diagnosis can also be made after a small sample of tissue is removed from the urinary tract during a procedure called a biopsy. After the diagnosis is made, the entire tumour is usually removed in a procedure called transurethral resection (TURBT). For larger tumours that involve the bladder or kidney, part or all of the organ may need to be removed in a procedure called a resection.
Low grade papillary urothelial carcinoma viewed under the microscope.
Approximately 50% of low grade papillary urothelial carcinomas will grow back after being removed. This is called a recurrence. Some tumours can change over time into a more aggressive type of cancer called high grade papillary urothelial carcinoma.
The pathologic stage for this type of cancer is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer. According to this system, all low grade non-invasive papillary urothelial carcinomas are given a tumour stage of pTa.