Ancillary Techniques in Histopathology Specimens

The vast majority of histopathology specimens can be adequately reported by close attention to careful gross description, dissection and block selection and microscopy of good quality formalin-fixed paraffin sections stained with haematoxylin and eosin. However, key ancillary techniques are also used in a proportion of cases (see Chapter 45). Some examples follow.

Frozen sections: Confirmation of parathyroidectomy, assessment of operative resection margins in cancer surgery, cancer versus inflammatory lesions at laparotomy.

Histochemical stains: Demonstration of mucin in adenocarcinoma, congophilia in amyloid and organisms (pyogenic bacteria, tubercle, fungus) in infection.

Immunofluorescence: Glomerular deposits in renal biopsies, deposition of immunoglobulin and complement in blistering skin disorders.

Immunohistochemistry: The surgical pathologist's "second H and E" is invaluable in assessing tumour type, prognosis and treatment, e.g., carcinoma (cytokeratins) versus malignant lymphoma (CD45) and malignant melanoma (S100), or better prognostic and hormone responsive breast cancer (oestrogen receptor positive). Tumour antigenic profile is also of use in specifying the site of origin for a metastasis, e.g., prostate carcinoma (PSA positive).

Electron microscopy: Valuable in renal biopsy diagnosis, and tumours where morphology and immunohistochemistry are inconclusive, e.g., malignant melanoma (pre-/melanosomes) and neuroendocrine carcinoma (neurosecretory granules).

Molecular and chromosomal studies: Immunoglobulin heavy chain and T cell receptor gene rearrangements in the confirmation of malignant lymphoma and the characterisation of various cancers (malignant lymphoma, sarcoma and some carcinomas, e.g., renal) by specific chromosomal changes.

Quantitative methods: Prognostic indicators include the Breslow depth of invasion in malignant melanoma, muscle fibre typing and diameter in myopathies and the mitotic activity index in breast carcinoma.

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