## Core Concept
Prostate-Specific Antigen (PSA) is a protein produced by the prostate gland. Elevated levels of PSA in the blood can indicate prostate cancer, prostatitis, or benign prostatic hyperplasia (BPH). Understanding the characteristics and clinical implications of PSA is crucial for the diagnosis and management of prostate-related conditions.

## Why the Correct Answer is Right
The correct answer, which is not provided, would typically relate to a specific characteristic or clinical use of PSA that is accurate. Generally, PSA is a tumor marker used for screening and monitoring prostate cancer. It is produced by prostate epithelial cells, and its level can rise in conditions affecting the prostate.

## Why Each Wrong Option is Incorrect
Without the specific options provided, a general approach to evaluating incorrect statements about PSA includes:
- **Option A:** If a statement claims PSA is exclusively produced by cancer cells, it would be incorrect because PSA is produced by both benign and malignant prostate tissues.
- **Option B:** If a statement suggests PSA levels are not affected by benign conditions, it would be incorrect because conditions like BPH and prostatitis can elevate PSA levels.
- **Option C:** If a statement implies PSA screening is not useful for early detection of prostate cancer, it would be incorrect as PSA screening, along with digital rectal examination (DRE), is a tool for early detection.
- **Option D:** If a statement claims that an elevated PSA level always indicates cancer, it would be incorrect because elevated PSA levels can result from non-cancerous conditions.

## Clinical Pearl / High-Yield Fact
A key point to remember is that while PSA is a valuable tool for screening and monitoring prostate cancer, an elevated PSA level does not always indicate cancer. Factors such as the rate of change of PSA levels over time (PSA velocity), the ratio of free to total PSA, and the results of a digital rectal examination can help differentiate between cancer and benign conditions.

## Correct Answer: D. Always indicates cancer.