**Core Concept**
Lethal midline granuloma is a rare and aggressive form of destructive facial lesion, characterized by the involvement of the nasal cavity and surrounding tissues. It is a type of natural killer (NK) cell lymphoma, specifically a subtype of the nasal type of extranodal NK/T-cell lymphoma.

**Why the Correct Answer is Right**
The correct answer is C. NK cells because lethal midline granuloma is primarily composed of NK cells that exhibit a clonal expansion and malignant behavior. This condition is often associated with Epstein-Barr virus (EBV) infection and is more common in Asia. The NK cells in lethal midline granuloma are characterized by their expression of CD56 and CD94, and their ability to produce cytokines and chemokines that contribute to the destruction of surrounding tissues.

**Why Each Wrong Option is Incorrect**
**Option A:** T-cells are not the primary cell type involved in lethal midline granuloma. While T-cells may be present in the tumor microenvironment, they are not the primary malignant cell type.
**Option B:** B-cells are not typically associated with lethal midline granuloma. This condition is not a type of B-cell lymphoma.
**Option D:** Macrophages are not the primary cell type involved in lethal midline granuloma. While macrophages may be present in the tumor microenvironment, they are not the primary malignant cell type.

**Clinical Pearl / High-Yield Fact**
Lethal midline granuloma is a rare and aggressive condition that requires prompt recognition and treatment. It is often associated with systemic symptoms such as fever, weight loss, and night sweats, and can be treated with a combination of chemotherapy, radiation therapy, and immunotherapy.

**✓ Correct Answer: C. NK cells**