Tis (in situ)

TIS (Carcinoma In Situ, CIS)

TIS (Tis) stands for Carcinoma In Situ, a high-grade, flat (non-papillary) tumor confined to the urothelium (innermost lining of the bladder). It is classified under the TNM staging system for bladder cancer as:

  1. Tis (TaTis): Pure CIS (no invasion).
  2. Tis + Ta/T1: CIS coexisting with papillary tumors.

Key Features of CIS

  1. Aggressive Nature:
    1. High-grade (HG) by definition.
    2. Not invasive but has a high risk of progression to muscle-invasive disease (~50% if untreated).
  2. Microscopic Appearance:
    1. Disorganized, malignant cells limited to the urothelium.
    2. No penetration into the lamina propria or muscle.
  3. “Field Effect”:
    1. Often multifocal (scattered across the bladder).
    2. May extend into prostatic urethra or upper tracts.

Clinical Presentation

  • Symptoms:
    • Irritative voiding (urgency, frequency, dysuria) – mimics UTI.
    • Hematuria (less common than with papillary tumors).
  • Diagnosis Challenges:
    • Invisible on cystoscopy (~30% of cases) → Requires random biopsies + urine cytology.
    • Positive urine cytology (key clue, especially with negative imaging).

Diagnosis

  1. Cystoscopy with Blue-Light/NBI (enhances CIS detection).
  2. Biopsies:
    1. Targeted (if visible lesions).
    2. Random (if suspicion persists despite normal appearance).
  3. Urine Tests:
    1. Cytology (high specificity for HG tumors).
    2. FISH (UroVysion), NMP22 (adjuncts).

Management

First-Line Treatment: BCG Immunotherapy

  • Induction: 6 weekly intravesical BCG instillations.
  • Maintenance: 3-week courses at 3, 6, 12, 18, 24, 30, and 36 months.
  • Response Rates:
    • Complete response (CR) in ~70% initially.
    • ~30–50% progress if BCG fails.

BCG-Unresponsive CIS Options:

  1. Pembrolizumab (Keytruda®) – FDA-approved (41% CR rate).
  2. Radical Cystectomy – Gold standard for refractory cases.
  3. Clinical Trials:
    1. Nadofaragene firadenovec (gene therapy).
    2. Vicinium (antibody-drug conjugate).

Prognosis

Why is CIS Dangerous?

  • Invisible lesions → Delayed diagnosis.
  • High recurrence/progression rates → Requires aggressive surveillance.
  • Predictor of poor outcomes if coexists with T1 tumors.

Takeaway

TIS (CIS) is a stealthy, high-risk bladder cancer variant requiring BCG immunotherapy and close monitoring. Early detection and treatment are critical to prevent muscle invasion.