Overall, all diagnostic strategies (NLBB, FNA, LCNB ultrasound and stereotactic guided) show comparable agreement rates. However, the miss rates differ: 2% for NLBB, 3% for COBRA (LCNB in study setting), 5% for FNA and 8–12% for LCNB in practice, respectively.
Ductal carcinoma in situ
underestimate (the finding of DCIS without invasive carcinoma in the diagnostic material, but with invasive carcinoma in the therapeutically specimen) varies from 8% (NLBB) to 37% (LCNB ultrasound guided). The difference in treatment of in situ
and invasive carcinoma with respect to the axilla makes this a serious clinical problem. Previous studies on the underestimation of DCIS in a diagnostic surgery show figures of 16 and 17% in a smaller series of patients (3 out of 19 and four out of 24) (Thompson et al, 1991
; Tartter et al, 1997
). Our figure of six out of 74 (8%) confirms the fact that DCIS underestimation is also a problem in diagnostic NLBB. Ductal carcinoma in situ
underestimation of LCNB has often been considered as a specific disadvantage of this technique, but every form of sampling, whether surgical or image-guided minimal invasive, deals with this problem. Therefore, the often results with respect to DCIS underestimation in nonsurgical biopsy studies have to be compared to the figures of surgical biopsies.
High-risk underestimate (the finding of ADH, lobular carcinoma in situ
without malignancy in the diagnostic material, but with carcinoma (in situ
or invasive), in the surgical specimen) varies from 9% (NLBB) to 40% (LCNB stereotactic guided). In the literature, figures of high-risk underestimate for 14-gauge needle biopsy range from 14 to 58%. (Jackman et al, 1999
; Verkooijen et al, 2000
) It is difficult to characterise the nonsurgical high-risk group as a whole. Most frequently, this group is being used for lesions with a microscopic pattern for which there is no consensus in classification or in cases where final classification is difficult or even impossible because of the small amount of tissue. Therefore, high risk is frequently being used as an ‘escape category’ for lesions difficult to diagnose (e.g. atypia at FNA and ADH at core biopsy). In case of a lesion classified as high risk, a larger amount of tissue is needed for final diagnosis.
In understanding the computed estimates, one should keep in mind two aspects of patient selection. First, the selection of primary diagnostic procedure in relation to the imaging characteristics, and second patient selection for the surgical histopathologic confirmation of the primary diagnostic procedure.
Fine-needle aspiration was only used with ultrasound guidance, and therefore in selected cases. This selection was based on the imaging characteristics of the lesion. Only 5.3% of the lesions diagnosed with FNA consisted only of microcalcifications. For the whole population, this figure was 30.6%. So, FNA was mainly used in cases of lesions not just consisting of microcalcifications. For the interpretation of the miss rate figures this is important to realise. It has been reported that miss rates are higher in lesions consisting of microcalcifications (Lifrange et al, 1997
). Fine-needle aspiration shows a high percentage of nonconclusive results (29%). This is a well-known major disadvantage of the technique. The reported rates for insufficient specimen with ultrasound-guided FNA vary from 0 to 38% for nonpalpable lesions (Klijanienko et al, 1998
). The success of FNA is operator dependent (Masood, 1998
). The best results have been reported with an experienced operator performing the aspirations. A multicentre clinical trial to evaluate FNA for nonpalpable lesions performed by multiple operators was terminated early because of the high rate of insufficient samples (Pisano et al, 1998
). Comparison of the two institutions where FNA was performed in our study shows a percentage of nonconclusive samples of 21.8% at the AvL and of 45.8% at the UMCU. At the AvL, FNA is performed by a small group of radiologists and dedicated cytopathologists. The results at the AvL compare well with previous results (Ciatto et al, 1997
). At the UMCU, the aspiration is performed by a large group of radiologists and residents. These high rates of insufficient samples as reported from the UMCU make its use impractical in a clinical setting, and supports the operator dependence as mentioned above. Another well-known problem of FNA is the fact that it is not capable of differentiating between in situ
and invasive carcinoma in this study, resulting in a DCIS overestimation rate (the finding of malignant cells on cytology, and DCIS without invasive carcinoma in the surgical specimen) of 9%. As mentioned above, the difference in treatment of in situ
and invasive carcinoma with respect to the axilla makes this a serious clinical problem.
For ultrasound-guided LCNB, the lesion selection based on the mammographic image was even more obvious. Only two cases (1.6%) consisted of only microcalcifications on mammography. Despite this selection, ultrasound-guided LCNB shows a relatively high miss rate of 12%. The result of ultrasound-guided LCNB in our study differs from the results in the literature on this subject. One study showed almost an equal accuracy with ultrasound-guided LCNB compared to NLBB, using a 14-gauge needle and a total of four to five passes (Parker et al, 1993
). The 18-gauge needle with two passes in our study was responsible for six of the eight misses. This technique is definitely inferior to the one Parker described and the one that was used in the COBRA study. There is a discussion in the literature about whether an 18-gauge needle is acceptable for ultrasound-guided LCNB (Cardenosa, 1999
). With respect to our figures, caution is warranted.
In stereotactic-guided LCNB, no selection was made. Half of the lesions consisted of microcalcifications only (50.7%). All three misses with stereotactic-guided LCNB were found in the group of lesions consisting of only microcalcifications. If we compare the two institutions where stereotactic-guided LCNB was performed, there is a clear difference in outcome. This is probably due to the technique used (18-gauge two to three passes (UMCN) vs
14-gauge with a minimum of five passes (UMCU)). The 18-gauge needle with two or three passes was responsible for 66.6% of the misses and 50% of the underestimated high risks. Although the number of cases with the 18-gauge needle is small, the figures are disappointing. A previous study showed that a 14-gauge needle provides the most accurate diagnosis, compared to 16- and 18-gauge needles (Nath et al, 1995
). Furthermore, the diagnostic sensitivity is improved by increasing the number of cores taken to six or more, particularly in women with mammographic microcalcifications of an equivocal nature (Rich et al, 1999
). The limitation in the assessment of the group ‘microcalcifications only’ indicates that a larger volume of tissue is necessary for a reliable histopathalogic diagnosis. Therefore, in both North America and many European breast diagnostic centres, vacuum-assisted core biopsy is now extensively used. This technique has the ability to obtain more diagnostic material during percutaneous biopsy compared to 14-gauge core biopsy.
The second important aspect of patient selection in our study (different from the COBRA, where all patients received a surgical histopathologic confirmation) is the selection that was made by surgeons of patients who underwent an ‘additional’ NLBB in cases of a benign result. It is reasonable to assume that those patients for whom the surgeon did not have a secure feeling about the benign primary diagnosis were selected for NLBB. And therefore, those patients not selected for subsequent NLBB have a correct primary diagnosis. Taking this into account, we computed the maximum agreement rates.
In conclusion, we found that FNA has a very high percentage of nonconclusive results and has no place in the diagnosis of lesions consisting of only microcalcifications. For the assessment of lesions consisting of microcalcifications only and to exclude malignancy in all other lesions, 18-gauge needle core biopsy is unsuited. Ultrasound-guided intervention can be performed in a large percentage of nonpalpable lesions. In a study setting, the dedicated prone table used in combination with state-of-the-art assessment protocols shows the best results. Lesions only consisting of microcalcifications on mammography need special attention.