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Histotechnology and Diagnostic Cytology

IDENTIFYING SURGICAL MARGINS

Marking surgical margins are often required for determining the adequacy of excision of lesions. Sometimes up to 6 margins (medial, lateral, superior, inferior, superial and deep margins) are required to be individually marked.

The properties of a good marker include:

• It is quick to dry.
• It is easy to apply.
• It has a long shelf life.
• It is cheap.
• It is non-toxic.
• It does not spread beyond the edge of the marked area.
• It is preserved during processing (no contamination of solutions).
• It is visible macroscopically and microscopically.
• Sectioning is not affected.
• It is radiolucent.
• There are multiple colours available.

India Ink, a colloidal suspension of particulate carbon in aqueous gum has been used for many years, but is messy, slow to dry and spreads readily over the tissue surface. 10% Silver Nitrate in methanol has been suggested but it also spreads over the surface and is macroscopically invisible.

Birch etal (J.Clin.Pathol 43:608-609, 1990) have suggested that specimens can be "dunked" into 1% aqueous alcian blue. This method is quick, cheap and the coating is radioluscent.

Harris (J.Clin.Pathol 43:346, 1990) has suggested the use of Tippex fluid. This is a solution of titanium dioxide and polyacrylate in trichloethane. It has a long shelf life, is easy to use, quick drying, non-toxic and the tissue processor is not affected. The marker does however have a tendency to lift and is radiodense.

Hunter-Craig etal (J.Clin.Pathol. 44:874-875, 1991) rolled bloted dry specimens in starch powder. The surface coating of starch is visible on light microscopy but strickingly apparent if crossed polarisers are used.

Artist's pigments in acetone (a 50% solution) were used by Patterson and Davies (J.Clin.Pathol 41:1013-1016, 1988). The pigments are quick drying, have a good range of different colours that are visible both macroscopically and microscopically (especially using polarised light) and are resistant to processing. They are however, radiodense and have a short storage life. It must be remembered that the dry powders (which contain cobalt, manganese and cadmium) are toxic. The pigment granules are also of similar size and density to microcalcification and there may be confusion on subsequent specimen mamography after tissue slicing. Suggested pigments are as follows:

Armstrong etal (J.Clin.Pathol., 43:604-607, 1990) have described the use of organically coloured gelatins, where 8% solution of dye is prepared in 24% aqueous gelatin. They found it easier to discriminate between colours of particulate dyes (ie plant substances), with the gelatin staining with both haematoxylin and eosin giving a pink to purple colour. They found clear demarcation between two adjacent colours and only a modest knowledge of botany was required for the identification of the three plant materials.

Unfortunately tumeric causes knife scratching.

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