Obtaining Cytological Histological Diagnosis

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Fine-needle aspiration sampling (FNA) for cytological diagnosis is a standard procedure for palpable nodules. Traditionally this is performed by inserting a green needle on a syringe into the palpated nodule. It is safe and accurate for most head and neck masses [14,15].

Ultrasound is now increasingly being used to position the needle more accurately by selecting a particular part of the nodule, for example the solid component of the wall in a mainly cystic nodule [16,17] or into impalpable nodules (Figure 26.7).A particular nodule can be chosen

Figure 26.7 Cutting needle biopsy of thyroid nodule.

Figure 26.6 Power Doppler (A) showing peripheral flow in a benign nodule (and the common carotid artery) and color Doppler (B) showing central intranodular flow in a malignant nodule.

where the features are suggestive of malignancy. This is often not the palpable nodule. The needle is advanced through the tissues with US visualization in real time. The nondiagnostic sample rate is significantly reduced [18,19]. Deeper and smaller nodules can easily be sampled [20,21]. As a result the availability of US-guided biopsy is seen as important in centers treating thyroid disease [6,18,22-27].

Although historically cutting needles have not been used in the neck due to the theoretical risk of damage to other tissues, when used with US guidance the dangers are extremely small. As such this is the routine method in our hospital for impalpable nodules, where there has been a failed previous FNA or for recurrent disease, that is, for the most difficult cases. There have been no major complications. A double spring action needle is preferred (the inner stylette and the outer cutting sheath are both fired by spring action) as the size of the sample obtained is maximized. The needle is fired on the touch of a button on the handle for a fixed distance (either 2.2 or 1.1 cm). Under local anesthetic and ultrasound vision the needle is advanced to the target nodule and the path of the needle once fired can be considered to hit the target and miss important structures. Cutting needles significantly improve the quality of the sample obtained for the cytologist, reducing the nondi-agnostic sample rate to less than 10% [27-29; Richardson et al., unpublished]. It is also a safe method of sampling neck lymphadenopathy [30]. Most patients who have had sampling performed using both methods ("blind" FNA and US-guided cutting biopsy) prefer the latter, in our experience.

Being able to position a needle precisely within the thyroid makes local injection of ethanol possible in the treatment of autonomous nodules and symptomatic cysts [31,32].

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