1. Electron Microscopy - Osler Institute Pathology Board Review Objectives Detect and recognize cytoplasmic organelles and matrix Interpret the ultrastructural features of commonly encountered tumors, non neoplastic entities and infectious agents Guide to tissue submission Undifferentiated malignant tumorsSmall cell malignancies Neuroendocrine tumorsCNS tumors Anomalous IHC resultsSelect IHC panel Eosinophilic granulomaRenal biopsies Heart biopsiesNerve biopsies Bullous diseases of skinStorage diseases Rapid diagnosis of viral infectionCiliary dysmorphology Extracellular matrix

2. Electron Microscopy - Osler Institute Pathology Board Review Processing tissue for electron microscopy 1 mm cubed tissue pieces Dehydrate, infiltrate, osmicate, embed in plastic Toluidine blue thick sections Thin sections – 100 nm on copper grids (silver sections) Interpretation of electron micrographs Determine approximate magnification Identify organelles Integrate ultrastructural features with clinical history, light microscopy, IHC and molecular diagnostics Limitations of electron microscopy Sample size Multidirectional differentiation No diagnostic organelles

3. Primer of Organelles Nucleus Abundant heterochromatin – Ewings sarcoma, B cell lymphomaEwings sarcoma Cerebriform nuclear contours Nuclear pseudoinclusions – nuclear pockets Intranuclear tubular aggregates Nucleolus Meandering reticular nucleoli – seminoma, dysgerminoma Marginated Nucleolus Increased nucleoli Electron Microscopy - Osler Institute Pathology Board Review Slide 3

4. Electron Microscopy - Osler Institute Pathology Board Review Primer of Organelles Cytoplasm Annulate lamellaeAnnulate lamellaeCylindrical confronting cisternae CytoskeletonEndoplasmic reticulum GolgiIntercellular junctions Lamellar cytoplasmic inclusionsLipid Langerhan’s cell granulesLysosomes MelanosomesMicrovilli MitochondriaRibosomes and polyribosomes Secretory granulesTubular reticular structures Weibel Palade bodies Extracellular Matrix Amyloid Collagen