Expansion
Renal biopsy, ciliary disorders, storage disease and undifferentiated tumours
Expansion
Preparation differs from light microscopy: glutaraldehyde fixation, osmium tetroxide, resin embedding, ultrathin sections of about 70 nanometres, and heavy metal staining with uranyl acetate and lead citrate.
Remaining diagnostic indications
- Renal biopsy: the location of immune deposits distinguishes the glomerulonephritides. Subepithelial in membranous nephropathy and post-streptococcal disease (humps), subendothelial in lupus, mesangial in IgA nephropathy. Podocyte foot process effacement defines minimal change disease
- Primary ciliary dyskinesia: absent dynein arms in the 9 plus 2 axoneme
- Storage disorders: characteristic lysosomal inclusions
- Undifferentiated tumours: melanosomes in melanoma, dense core granules in neuroendocrine tumours, desmosomes in carcinoma
- Amyloid: non-branching fibrils of 8 to 10 nanometres
- Muscle and nerve biopsy
Largely superseded by immunohistochemistry and molecular methods for most tumour diagnosis, since these are faster, cheaper and more specific.
Scanning electron microscopy gives surface topography rather than internal structure, and is used more in research than in diagnosis.