**Core Concept:** Nurse cells are a phenomenon observed in certain cancer cells where they surround and protect the tumor cells from the host immune system, thereby promoting tumor growth and evading immune detection.

**Why the Correct Answer is Right:** Nurse cells are a unique feature of certain cancer cells, specifically the ones found in malignant mesothelioma. These cells, known as mesothelial cells, form a protective barrier around the tumor cells, which prevents immune cells from recognizing and attacking the tumor. This allows the cancer cells to grow undetected and evade immune surveillance, contributing to tumor progression.

**Why Each Wrong Option is Incorrect:**
A. Mesothelial cells are not involved in the formation of nurse cells in other types of cancer cells.
B. Neutrophils, which are immune cells, are not responsible for creating nurse cells.
C. Stromal cells are not the primary cells involved in nurse cell formation. Nurse cells are primarily composed of mesothelial cells.
D. Mesenchymal cells are not the primary cells responsible for forming nurse cells in malignant mesothelioma.

**Clinical Pearl / High-Yield Fact:** Understanding nurse cells in malignant mesothelioma is crucial for understanding cancer progression and immune evasion. Recognizing this phenomenon can aid in developing targeted therapies that disrupt the nurse cell formation, potentially enhancing cancer treatment outcomes.

**Correct Answer:** **C.** Nurse cells are primarily composed of mesothelial cells.