**Core Concept**
BCG (Bacillus Calmette-Guérin) is a live, attenuated vaccine strain of Mycobacterium bovis, used in the treatment of certain diseases. It has immunomodulatory properties, stimulating the immune system to attack and eliminate malignant cells.

**Why the Correct Answer is Right**
BCG is primarily used in the treatment of superficial bladder cancer, specifically carcinoma in situ (CIS) and high-grade Ta tumors. It works by inducing a strong immune response, which helps to eliminate cancer cells from the bladder mucosa. BCG is administered intravesically, directly into the bladder, where it stimulates the activation of immune cells, such as macrophages and T lymphocytes, which then target and destroy cancer cells. The exact mechanism involves the recognition of BCG components by pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), which triggers the activation of immune cells.

**Why Each Wrong Option is Incorrect**
**Option A:** BCG is not used as a treatment for tuberculosis; it is a vaccine against tuberculosis, used to prevent the disease, not to treat it.
**Option C:** BCG is not used to treat anthrax; anthrax is caused by Bacillus anthracis, a different bacterium altogether.

**Clinical Pearl / High-Yield Fact**
BCG treatment for bladder cancer requires a specific regimen, typically involving 6-12 weekly instillations of BCG, and monitoring for side effects such as hematuria, dysuria, and fever.

**✓ Correct Answer: B. Treatment of superficial bladder cancer**