**Core Concept**
Genital tuberculosis (TB) in male patients is a form of extrapulmonary TB that affects the genitourinary system. It is caused by the bacterium *Mycobacterium tuberculosis*, which typically spreads through hematogenous dissemination from a primary focus in the lungs.

**Why the Correct Answer is Right**
Genital TB preferentially affects the epididymis due to its rich blood supply and the predilection of *M. tuberculosis* to infect areas with high oxygen tension. The epididymis is a long, coiled tube that stores and transports sperm from the testes, and its involvement can lead to symptoms such as pain, swelling, and infertility. The infection can also spread to the testes, prostate gland, and seminal vesicles, causing a range of clinical manifestations.

**Why Each Wrong Option is Incorrect**
**Option A:** The vas deferens is not the primary site of involvement in genital TB, although it can be affected in some cases.
**Option B:** The prostate gland can be involved in genital TB, but it is not the preferential site of infection.
**Option C:** The seminal vesicles can be affected in genital TB, but they are not the primary site of involvement.

**Clinical Pearl / High-Yield Fact**
Genital TB can present with a range of symptoms, including epididymitis, orchitis, and infertility, and can be challenging to diagnose due to its nonspecific presentation.

**Correct Answer:** C. Prostate gland