**Question:** All are true about Glomus body tumor except -

A. Glomus body tumor is a benign tumor arising from smooth muscle cells (smooth muscle tumors).
B. Glomus body tumor is a malignant tumor arising from smooth muscle cells (smooth muscle tumors).
C. Glomus body tumor typically occurs in the head and neck region.
D. Glomus body tumor is caused by mutations in the RAS gene (RAS oncogenes).

**Core Concept:** Glomus body tumor is a rare and benign tumor that develops from the smooth muscle cells of the glomus body, a small, involuntary blood vessel found in the dermis. The glomus body is responsible for thermoregulation and sensation of temperature in the skin.

**Why the Correct Answer is Right:**
Option D is correct because Glomus body tumors are not caused by mutations in the RAS gene (RAS oncogenes). Instead, these tumors are thought to arise from the glomus body smooth muscle cells due to unknown genetic or environmental factors. While mutations in the RAS gene are involved in certain types of cancer, they are not directly responsible for Glomus body tumors.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because Glomus body tumors are benign (non-cancerous) lesions. Smooth muscle tumors are generally classified as either benign (e.g., leiomyomas) or malignant (e.g., leiomyosarcoma).

B. This option is incorrect because Glomus body tumors are benign (non-cancerous) lesions. Malignant tumors are typically characterized by uncontrolled cell growth and invasion into surrounding tissues, which is not the case for Glomus body tumors.

C. This option is incorrect because Glomus body tumors can occur in various body parts, not just the head and neck region. They may arise from the dermal glomus body in the extremities, trunk, or genitourinary system. However, the tumor may be more apparent in the head and neck region due to the prominence of the glomus body in this area.

**Core Concept:** Glomus body tumors are benign (non-cancerous) tumors that develop from the smooth muscle cells in the glomus body. The glomus body is a small, involuntary blood vessel found in the dermis, responsible for thermoregulation and thermosensation of the skin.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because Glomus body tumors are benign (non-cancerous) lesions. Malignant tumors develop from abnormal cell growth and invasion into surrounding tissue.

B. This option is incorrect because Glomus body tumors are benign (non-cancerous) lesions. Malignant tumors are characterized by uncontrolled cell growth and invasion into surrounding tissues, which is not the case for Glomus body tumors.

C. This option is incorrect because Glomus body tumors can occur in various body parts, not just the head and neck region. They may arise from the dermal glomus body in the extremities, trunk, or genitourinary