## Pancreatic Islets of Langerhans: Histological Identification ### Characteristic Features **Key Point:** Islets of Langerhans are identified as **pale-staining (basophilic), rounded cell clusters** that are **clearly demarcated from the surrounding acinar tissue** by a thin connective tissue capsule. ### Microscopic Architecture **High-Yield:** The islets appear as: - **Rounded or oval clusters** of endocrine cells - **Pale/light staining** due to high metabolic activity and abundant ribosomes (basophilia) - **Well-vascularized** with a rich capillary network - **Separated from exocrine pancreas** by a delicate reticular fibre capsule - **Comprise ~1–2% of pancreatic mass** but receive ~10% of blood flow ### Comparative Table: Pancreatic Tissue Types | Feature | Islets of Langerhans | Acinar Tissue | | --- | --- | --- | | **Staining** | Pale/basophilic | Acidophilic (pink) | | **Cell arrangement** | Clustered, rounded | Acini around ducts | | **Secretory granules** | Hormone granules (small) | Zymogen granules (large) | | **Capsule** | Reticular fibre capsule | No distinct capsule | | **Vascular supply** | Very rich (10% of flow) | Moderate | ### Clinical Pearl In routine H&E staining, islets appear as **pale islands** surrounded by the darker, more acidophilic acinar tissue—hence the term "islet" (island). Immunohistochemistry with anti-insulin, anti-glucagon, and anti-somatostatin antibodies definitively identifies cell types within the islet. 
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