Diagnostic outcome of two different CT-guided fine needle biopsy procedures

Fine needle biopsy is a well established and a commonly used procedure in tumour diagnostics. In addition to the conventional endoscopic and percutaneous fine needle punctures there is an increasing interest in the use of flexible endosonographic ultrasound giuded fine needle aspiration biopsies. Based on the main technical principle the large number of different needles can be grouped into core-, cutting- and aspiration needles. Core- and cutting needle specimens are generally suitable for embedding and histological analysis, while aspiration needle specimen comprise most often smaller cell and tissue fragments, which should be evaluated by cytology. It has to be considered that most needles work by applying at least two functional principles; e.g. a YN both cuts and aspirates. Despite the long tradition of fine needle biopsy diagnostics, very little is known about the exact mechanisms that influence the quality and the outcome of the procedure.

The aim of the present study was therefore to answer the following questions: (1) Which are the technical factors relevant for successful use of RSN and YN? (2) What is the rate of adverse events using RSN and YN? (3) What is the diagnostic outcome of CT-guided RSN- and YN-punctures in benign and malign thoracic lesions?

In order to optimize the outcome of fine needle biopsy it is important to keep in mind, that all needles basically work like cutting instruments. Here we were able to show, that first of all the extend of needle movements raise the cell/tissue recovery and result in a high diagnostic outcome of CTFNP, which is even comparable with other conventional bioptic procedures. Both sensitivity and specificity, as well as complication rates were largely independent of needle type and bioptic technique.

In the recent years, cytology of the respiratory tract has been revolutionized by a high degree of sophistication in radiologic technology and sonography, making a precise visualization and localization of tumours in the lungs, bronchi, mediastinum or chest wall possible. Between 1997 and 2005 the files of the hospital Großhandorf cytology laboratory recorded a total of 9380 fine needle specimens (4847 rapid on site analysis). Basically any patient found to have a demonstrable radiolographic tumour is a potential candidate for a fine needle biopsy. A further decision on whether or not to proceed with this procedure is usually based on the morphologic evidence provided by prior cytologic and histologic specimens obtained from the respiratory tract and on the clinical relevance of morphological findings.

From all fine needle specimens several direct smears are prepared and air dryed. One of these smears will be chosen for rapid or standard Giemsa staining. Because of direct sampling within the tumour by a fine needle, these specimen most often contain large numbers of cancer cells and tissue fragments, leaving generally additional unstained slides for further routine- or immuncytological staining procedures. Despite that, the amount of material as well as the number of slides are usually limited and occasionally there are 9 patients (2.6 % in our case), in whom a cancer is suspected but can not be conclusively diagnosed by cytology alone.

In pneumology CTFNP are well established diagnostic procedures and in clinical practise a number of different needles are used. Despite of all technical differences all fine needles have in common that they function like a cutting instrument. In addition, turning and repeated puncture movements help to gain small cell clusters and tissue fragments. Although a applied negative pressure can assist in raising the amount of cells, this factor is of limited importance compared to the effect of cutting. This would explain that although a large differences in negative pressure between needle types exist (fig. 1), we found a similar diagnostic outcome with NN and YN. In addition, the number and handling of repeated punctures influenced the success of a fine needle biopsy, as we were able to show in our experiments with pig spleen (fig. 2).

The sensitivity and the diagnostic outcome of fine needle biopsy seems to be independent from the kind of morphological analysis (histology or cytology) and have been reported to range between 62%–83% (at a specificity of 100%) and 68%–85%, respectively [1–3]. Both with the YN and the RSN, which were used in this study, we found a very similar diagnostic outcome of 77 % as compared to the literature [4–6]. CTFNP therefore did not differ from conventional cut needle or forceps biopsies [7]. The diagnostic outcome, however, depends on the size of the target. In line with others [1] we also found that the increase of the diagnostic outcome corresponded to the tumour volume (table 3). This would also explain better values for sensitivity and specificity in group of patients with clinically verified tumours, as these tend to be larger in size as compared to those with histologically verified final diagnosis (table 2).

The most common complication of CTFNP are haemorrhage or the occurrence of a potentially drainage requiring pneumothorax. It is well known that the risk of such complications increase with the outer diameter of the needle. Using fine needles with a diameter > 1 mm leads to pneumothorax rates of more than 13 % [3, 8]. Experienced clinicians, on the other hand, are able to keep the complication rate significantly lower, especially if needles with smaller calibre are used. In our study we recorded adverse events in only 6 % of all cases, with no differences between RSN and YN, which is in accordance with [4].

As shown in table 1 there are quite large differences in the costs of different needle types. We would like to emphasise that a clinician should always be working with a needle type he is familiar/experienced with, as, in the time of restricted hospital budgets, it could be argued that only low price needles should be used. With respect to the complication rate it is our experience that it increases with larger needles. In line with the literature we would therefore also recommend needles with outer diameter below 0.8 mm [8].

In summary we would like to emphasize that a fine needle basically works like a cutting instrument, and repeated needle movements are of prime importance for both cells/tissue quantity and quality. In line with others we found that the diagnostic outcome of CTFNP was high. In addition we were able to demonstrate that the outcome was largely independent of needle type and bioptic technique, and comparable with other conventional bioptic procedures.