Basic Pathology

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1.1 Normal appendix wall. Mucosa (white arrow) : glandular covering epithelium (arrowheads)  and crypts ( angular arrows ). Submucosa (red arrow) : connective and lymphoid tissue , the latter forming follicles ( curved arrows). Muscular layer (green arrow) . Subserosa (yellow arrow). In haematoxylin – eosin stain, haematoxylin is basophilic and stains cell nuclei whereas eosin is acidophilic and stains cell cytoplasm. Mature small lymphocytes have very little cytoplasm and thus are basophilic – purple; on the contrary, muscle cells (green arrow) have abundant cytoplasm so as to contract and thus are acidophilic – pink.

Read more: Acute appendicitis
 
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2.1 Gallbladder mucosa. Glandular epithelium (white arrows) and basophilic lamina propria (purple arrows)  due to presence of inflammatory cells with little cytoplasm.

Read more: Acute cholocystitis
 
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3.1 Duodenum ulcer.  Mucosal glandular epithelium (white arrows) . Area of epithelial loss (black arrows) and formation of inflammatory granulation tissue (red arrows).

Read more: Ulcerative lesions
 
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4.1 A large bronchiole at the centre with its epithelial lining (white arrows, respiratory-type, cylindrical  epithelium) and smooth muscle tissue (green arrows) around its wall. Alveoli filled with inflammatory exhudate (asterisks) instead of air. The exhudate has come out of the capillaries in the diaphragms (arrowheads) between the alveoli.

Read more: Lobular pneumonia – lung abscess
 
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ANDREAS C. LAZARIS

Neoplasia is characterized by uncontrolled cellular growth owing to increased cellular proliferation and/or decreased apoptosis. If the neoplasm grows without invading its stroma and surrounding tissues ,it is of benign nature and the disease is local. If the growing neoplasm invades its stroma and surrounding tissues gaining access to lymph vessels or blood vessels, it acquires metastatic potential so the disease is potentially systemic, not only local.  When we examine all neoplasms microscopically, we look for signs of differentiation ie, their resemblance to   normal tissues so as to define their histogenesis and classify them , since the tissue towards which a neoplasm differentiates is generally  identical to the tissue from which it derives. Only in malignant tumours,  the degree of differentiation is reported as the histologic grade of malignancy. In benign tumors which are not fully differentiated and exhibit some degree of cellular atypia , we grade their degree of cellular dysplasia. Benign tumors are not staged since, due to their benign nature  , they are incapable of metastasizing . On the contrary, malignant tumours are staged according to the extent of their dissemination at the time of their diagnosis.

Read more: Hipon images on neoplasia