Which of the following is the hallmark histological feature of granulomatous inflammation?

Question

Accepted Answer

B. Epithelioid histiocytes arranged in a granuloma with or without central caseous necrosis. ## Hallmark of Granulomatous Inflammation

**Key Point:** The defining histological feature of granulomatous inflammation is the **granuloma** — a collection of activated macrophages (epithelioid cells) often arranged in a nodule, frequently with multinucleated giant cells and a surrounding rim of lymphocytes.

### Granuloma Structure

| Component | Description |
|-----------|-------------|
| **Epithelioid histiocytes** | Activated macrophages with elongated nuclei and pale cytoplasm; arranged in a palisade pattern |
| **Langhans giant cells** | Multinucleated giant cells with peripherally arranged nuclei in a horseshoe pattern |
| **Central necrosis** | Caseous (cheese-like) necrosis in tuberculosis; non-caseating in sarcoidosis, berylliosis |
| **Lymphocytic rim** | Surrounding T lymphocytes and fibroblasts |

**High-Yield:** Granulomatous inflammation is a **chronic response** to poorly degradable antigens or irritants. It represents a failure of the innate immune system to eliminate the offending agent, leading to persistent macrophage activation and organization into granulomas.

### Distinction from Other Inflammatory Patterns

- ~~Neutrophilic infiltrate~~ — characteristic of acute inflammation, not granulomatous
- ~~Plasma cells and Russell bodies~~ — seen in chronic non-granulomatous inflammation (e.g., chronic gastritis)
- ~~Fibroblastic proliferation~~ — occurs in the resolution phase but is not the hallmark feature

**Clinical Pearl:** The presence or absence of caseous necrosis helps differentiate causes: TB (caseating) vs. sarcoidosis (non-caseating).

Answer

A. Predominantly neutrophilic infiltrate with fibrin deposition

Answer

C. Lymphocytic infiltration with plasma cells and Russell bodies

Answer

D. Fibroblastic proliferation with collagen deposition

Which of the following is the hallmark histological feature of granulomatous inflammation?

Explanation

Hallmark of Granulomatous Inflammation

Granuloma Structure

Distinction from Other Inflammatory Patterns

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Component	Description
Epithelioid histiocytes	Activated macrophages with elongated nuclei and pale cytoplasm; arranged in a palisade pattern
Langhans giant cells	Multinucleated giant cells with peripherally arranged nuclei in a horseshoe pattern
Central necrosis	Caseous (cheese-like) necrosis in tuberculosis; non-caseating in sarcoidosis, berylliosis
Lymphocytic rim	Surrounding T lymphocytes and fibroblasts