Bladder cancer is a malignant neoformation arising from the mucosa (transitional epithelium) lining the urinary bladder. There are different types of bladder cancer depending on the malignancy of the cells that make up the tumor.
The bladder is a hollow organ formed by a smooth muscle (detrusor) whose function is to store urine between micturitions. The epithelium that lines it has a very particular characteristic and that is its total impermeability. This characteristic of the bladder mucosa or epithelium prevents toxic or irritating substances that are eliminated through urine from penetrating the detrusor muscle and from there to the rest of the organism.
Bladder cancer is an abnormal and disordered growth of this mucosa. Urology distinguishes three types of bladder cancer:
- Transitional carcinoma: is the most common and is derived from the transitional cells that line the bladder wall.
- Squamous cell carcinoma: a neoformation that begins in squamous cells, which are thin, flat cells that can form in the bladder after infection or prolonged irritation.
- Bladder adenocarcinoma: A very rare type of bladder cancer that begins in the glandular (secretory) cells that are in the lining of the bladder.
Depending on the malignancy of the cells that make up this tumor, bladder cancer is classified into three grades (G):
- G1: This is a well-differentiated tumor. The tumor cells are very similar to normal cells and are of low malignancy.
- G2: A moderately differentiated tumor. The tumor cells have features different from those of origin. It is of intermediate malignancy.
- G3: This tumor is poorly differentiated. The cells are very different from those of origin and have a high degree of malignancy.
The International Union of Cancer makes the most accepted classification of this type of tumors worldwide, which is called TNM classification. This classification consists of two main groups:
The first group is superficial bladder carcinomas. There are three types of tumors: Ta, Tis and T1.
- Ta: non-invasive papillary carcinoma or carcinoma confined to the mucosa.
- Tis: carcinoma in situ. Flat superficial tumor that respects the lamina propria.
- T1: tumor invading subepithelial connective tissue or invading the lamina propria.
The second large group of tumors are infiltrating bladder carcinomas: T2, T3 and T4.
- T2: tumor invading the muscular layer of the bladder.
- T3: tumor invading beyond the muscular layer or invading the perivesical fat.
- T4: tumor invading structures adjacent to the urinary bladder. It is divided into two:
Bladder cancer treatments
The type of treatment depends on the type of tumor diagnosed. The highest category of T and G detected in the bladder defines the treatment.
- Ta-T1 tumors: these tumors are treated endoscopically by transurethral resection. The goal of treatment should be the prevention of recurrence and progression.
- Tis (carcinoma in situ): can be treated in most cases with bladder instillations of bacilli Calmett-Guerin (BCG).
- Superficial but highly malignant tumors (T1G3) have a high tendency towards progression. They are usually treated by transurethral resection and bladder instillations of BCG. They are cases that must be closely monitored and where cystectomy, i.e. total removal of the bladder, plays an important therapeutic role.
- T2 or larger tumors are infiltrating tumors and cystectomy is necessary in most cases.
- Disease with pelvic adenopathy (N+) or distant metastases requires a different treatment scheme associated with chemo- and radiotherapeutic oncologic treatments.