Chapter 5 Discussion Questions and Answers

5.1 Discuss the complementary role of special stains and immunocytochemistry.

Special stains and immunocytochemistry are complementary because they are used to demonstrate different aspects of pathology within the tissue. Not all cases will require both but they may be appropriate to investigate pigments in skin samples or microorganisms in lung biopsy or GI samples.

5.2 Discuss the histological features seen on H&E staining that may indicate the need for stains to demonstrate infective agents.

Special stains for infective agents may be indicated if the tissue shows signs of an inflammatory response.

5.3 Discuss the value of mucin stains in the diagnosis of metaplasia.

Metaplasia is a change in cell type due to a stimulus. Therefore if a patient is suffering from acid reflux, the oesophagus will undergo metaplastic change to gastric type mucosa. The mucin staining pattern will therefore change from acidic mucins of the oesophageal specimen to neutral mucins of the stomach.

5.4 Discuss the role of special stains in the diagnosis of liver disease.

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5.5 Describe the investigative tinctorial and histochemical stains and what they demonstrate in muscle biopsies.

These should include:

  • H&E for general morphological detail, fibre basophilia and inflammatory features.
  • The use of a modified Gomori trichrome (GT) stain will help to identify ragged fibres, nemaline rods and tubular aggregates, cylindrical and cytoplasmic l bodies, rimmed vacuoles and general connective tissue abnormalities.
  • Oil red O will help identify neutral lipids and droplets of intrafibre lipid.
  • PAS with and without diastase will help to identify glycogen and necrotic fibres.
  • The enzyme histochemical stains nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) will identify cores and target fibres, lobulated fibres and fibre types I and II.
  • Succinic dehydrogenase (SDH) will help identify mitochondria.
  • Cytochrome oxidase (COX) will show mitochondria and COX deficiency. COX-SDH will identify COX-negative fibres.
  • Adenosine triphosphatase (ATPase at pH 10.4, 4.6 and 4.3) will distinguish between fibre types I, IIA , IIB and IIC.
  • Acid phosphatase will identify lysosomal activity, lipofuscin and macrophages.
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