**Core Concept**
Gleason scoring is a method used to grade prostate cancer based on its microscopic appearance. The system was developed by Dr. Donald Gleason in the 1960s and is widely used to predict the aggressiveness and prognosis of prostate cancer.

**Why the Correct Answer is Right**
Gleason scoring is done by examining the histological pattern of prostate cancer cells and assigning a score based on the percentage of cells in each pattern. The score ranges from 2 to 10, with higher scores indicating more aggressive cancer. The score is calculated by adding the grades of the two most prevalent patterns of cancer cells. This scoring system helps clinicians to predict the potential for cancer spread and guide treatment decisions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Gleason scoring is not used for breast cancer. Breast cancer is graded using the Nottingham histologic score, which assesses the histological features of the tumor.

**Option B:** This option is incorrect because Gleason scoring is not used for thyroid cancer. Thyroid cancer is graded based on the degree of cellular differentiation and the presence of nuclear features such as pleomorphism and mitoses.

**Option C:** This option is incorrect because Gleason scoring is not used for renal cell carcinoma. Renal cell carcinoma is graded based on the degree of cellular differentiation and the presence of nuclear features such as pleomorphism and mitoses.

**Clinical Pearl / High-Yield Fact**
It's essential to note that Gleason scoring is not a perfect predictor of prostate cancer behavior, and other factors such as patient age, PSA level, and lymph node status should also be considered when making treatment decisions.

**Correct Answer:** D. Prostate cancer.