## Metaplasia vs Dysplasia: Key Discriminator ### Core Distinction **Key Point:** Reversibility is the fundamental feature that distinguishes metaplasia from dysplasia. Metaplasia is an adaptive, reversible change in response to chronic irritation, whereas dysplasia is a pre-malignant, potentially irreversible alteration of cellular growth. ### Comparative Table | Feature | Metaplasia | Dysplasia | |---------|-----------|----------| | **Reversibility** | Fully reversible if stimulus removed | Irreversible; progresses toward malignancy | | **Nuclear changes** | Minimal; nuclei appear normal | Marked pleomorphism, hyperchromasia, coarse chromatin | | **Mitotic activity** | Normal mitotic rate | Increased mitoses, many abnormal | | **Architecture** | Preserved; organized epithelium | Disorganized; loss of stratification | | **Malignant potential** | None | High; precancerous lesion | | **Mechanism** | Adaptive response to chronic irritation | Clonal expansion of genetically altered cells | ### Clinical Examples **Metaplasia:** - Barrett's esophagus (columnar epithelium replacing squamous) → reverses if reflux controlled - Intestinal metaplasia of gastric mucosa → may regress with H. pylori eradication - Squamous metaplasia in bronchi (smoking) → can improve with smoking cessation **Dysplasia:** - Cervical intraepithelial neoplasia (CIN) → does not regress spontaneously - Barrett's esophagus with dysplasia → high risk of adenocarcinoma - Oral submucous fibrosis with dysplasia → irreversible progression ### High-Yield Point **High-Yield:** On histology, dysplasia shows loss of maturation, crowded nuclei with increased nuclear:cytoplasmic ratio, and disorderly arrangement. Metaplasia shows orderly, mature epithelium of a different type — the cells look normal, just in the wrong location. ### Clinical Pearl **Clinical Pearl:** If a chronic irritant is removed and the lesion regresses → it was metaplasia. If it persists or progresses despite removal of the stimulus → it is dysplasia or has already transformed to carcinoma.
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