Needle biopsy

This allows for a core of tissue to be removed at a depth. The most usual needle is the Trucut (Travenol) instrument (Fig. 6.9). The lesion and its depth must be confirmed. Adjacent important structures must not be at risk. The skin is cleaned and a bleb raised with local anaesthetic. A nick is then made with a sharp-pointed scalpel at the insertion point of the needle. With the fingers of one hand, the lump is fixed, if necessary, while inserting the closed needle into it. The cannula is held still while the stylette (which has a flattened area behind the sharp tip into which some tissue bulges) is advanced. The stylette is held still and the needle advanced over it, cutting off a thin core of tissue that bulges into the flat part of the stylette. The needle is kept closed and withdrawn to reveal the excised core of tissue which is gently placed in the fixative. As a rule the entry point in the skin requires a simple dressing only.

Figure 6.7. Elliptical biopsy. On the left, an ellipse is marked out with its long axis parallel to the skin tension lines. A boat-shaped full-thickness specimen is excised. If necessary, the edges are undermined to allow linear closure without tension.

Figure 6.9. Trucut needle biopsy. (a) The stylette, enclosed within a hollow needle, has a thinned segment. (b) when the needle reaches the lesion, it is held still while the stylette is advanced into the lesion. (c) The stylette is then held still while the needle is advanced, cutting off the tissue that has bulged into the thinned segment. (d) The closed needle and stylette are withdrawn, the needle is drawn back, freeing the biopsy specimen.

Figure 6.9. Trucut needle biopsy. (a) The stylette, enclosed within a hollow needle, has a thinned segment. (b) when the needle reaches the lesion, it is held still while the stylette is advanced into the lesion. (c) The stylette is then held still while the needle is advanced, cutting off the tissue that has bulged into the thinned segment. (d) The closed needle and stylette are withdrawn, the needle is drawn back, freeing the biopsy specimen.

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