## **Core Concept**
The question tests knowledge of prostate cancer metastasis patterns, specifically lymph node involvement. Prostate cancer typically spreads through lymphatic drainage. Understanding the lymphatic drainage of the prostate is crucial for determining the most common sites of lymph node metastasis.

## **Why the Correct Answer is Right**
The correct answer, **external iliac, internal iliac, and obturator lymph nodes**, is based on the lymphatic drainage of the prostate gland. The prostate gland primarily drains into the pelvic lymph nodes, which include the external iliac, internal iliac (also known as hypogastric), and obturator lymph nodes. These nodes are the primary sites for lymphatic spread of prostate cancer due to their proximity and direct lymphatic connections to the prostate.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify the correct groups of lymph nodes involved in prostate cancer metastasis.
- **Option B:** This option might be incorrect for similar reasons as Option A, not accurately representing the primary lymph nodes involved.
- **Option C:** Although not directly provided, any option not specifying **external iliac, internal iliac, and obturator lymph nodes** would be incorrect based on the accurate lymphatic drainage pattern of the prostate.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the lymphatic drainage of the prostate is primarily to the pelvic lymph nodes. This knowledge is essential for the staging and management of prostate cancer. The obturator lymph nodes are particularly significant as they are often one of the first sites of metastasis.

## **Correct Answer:** . **External iliac, internal iliac, and obturator lymph nodes**