muscleinvasive

Muscle-invasive refers to cancers that have grown through the innermost layers of an organ and into the muscular layer. In oncology, the term is most commonly applied to bladder cancer, where it denotes invasion of the muscularis propria (the detrusor muscle) by tumor cells. This is contrasted with non-muscle-invasive bladder cancer, which is confined to the mucosa or to the lamina propria without muscle invasion. In the TNM staging system for bladder cancer, muscle-invasive disease corresponds to T2 or higher.

In bladder cancer, distinguishing muscle-invasive disease is important because it carries a higher risk of progression and metastasis and typically requires more aggressive treatment than non-muscle-invasive disease. Stage T2 means the tumor has invaded the detrusor muscle, with T2a and T2b representing invasion of the inner and outer halves of the muscle, respectively. T3 indicates invasion into perivesical fat, and T4 indicates invasion into adjacent organs or structures. Lymph node involvement (N) and distant metastases (M) further determine prognosis and treatment strategy.

Diagnosis usually involves cystoscopy and transurethral resection of bladder tumor (TURBT) to determine whether muscle invasion is present, supported by imaging such as CT or MRI. Urinary cytology may be less informative for muscle-invasive disease.

Treatment commonly includes cisplatin-based neoadjuvant chemotherapy followed by radical cystectomy with pelvic lymph node dissection and urinary diversion; or bladder-preserving approaches such as trimodal therapy (TURBT with concurrent chemoradiation) in selected patients. Adjuvant therapy and careful surveillance are tailored to pathologic findings and overall health. Prognosis depends on stage, nodal status, response to therapy, and other patient factors.