**Core Concept**
RS cells, also known as Russell bodies, are inclusions found in the cytoplasm of plasma cells. They are composed of immunoglobulin light chains and are a hallmark of plasma cell dyscrasias, particularly in the context of multiple myeloma.

**Why the Correct Answer is Right**
RS cells are formed due to the accumulation of misfolded immunoglobulin light chains in the endoplasmic reticulum of plasma cells. This accumulation leads to the formation of inclusions, which eventually mature into Russell bodies. The presence of RS cells in plasma cells is a diagnostic feature of plasma cell dyscrasias, such as multiple myeloma, and can be detected using immunohistochemical staining.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as RS cells are not typically associated with lymphocytes, which are a different type of immune cell.
**Option B:** This option is incorrect as RS cells are not a feature of chronic inflammation, which is characterized by the presence of inflammatory cells and tissue damage.
**Option C:** This option is incorrect as RS cells are not a feature of normal plasma cell function, but rather a sign of abnormal plasma cell behavior.

**Clinical Pearl / High-Yield Fact**
RS cells are a key diagnostic feature of plasma cell dyscrasias, including multiple myeloma. The presence of RS cells in plasma cells can be detected using immunohistochemical staining and is an important diagnostic tool in the evaluation of patients with suspected plasma cell dyscrasias.

**Correct Answer:** D.