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Tristán Associates Harrisburg, PA 17111
Darling et al. [1] report their frequency of histologic underestimation in stereotactic breast biopsy and provide a review of the literature on this subject. Like many of us, they currently perform stereotactic biopsy exclusively with the 11-gauge Mammotome (Ethicon Endo-Surgery, Cincinnati, OH).
Darling et al. [1] take an average of nine samples and acknowledge having a histologic underestimation rate higher than that of other workers [2,3,4,5] who average 14-27 samples. However, Darling et al. seem to have missed the inescapable conclusion of that comparison: that taking more samples might improve their results. In no fewer than four places in their article, the authors specifically acknowledge that additional sampling might have been beneficial. For example, "Other factors such as lesion size, biopsy technique, and patient age are comparable; therefore, [our] lower average number of specimens obtained may again account for the higher rate of underestimation that we report...." Yet they apparently have no plans to change their habits: "At this point, our practice is to obtain an average of nine core specimens...."
Although differences in the number of cases in the studies could contribute to the differing underestimation rates, Darling et al. [1] would do well to emulate the technique of others and take more than the average of nine samples that they currently take. No multiinstitutional prospective trial is needed; in fact, Darling et al. must have already concluded that more tissue is better because they use only the 11-gauge Mammotome for stereotactic biopsy. No clinical trial prompted them to abandon the 14-gauge Mammotome in favor of the larger 11-gauge device. Why not simply take the logical next step and take more samples?
One of the few recognized shortcomings of minimally invasive biopsy is histologic underestimation, which potentially makes minimally invasive biopsy a wasted procedure. When infiltrating carcinoma is underestimated at minimally invasive biopsy as atypical ductal hyperplasia or ductal carcinoma in situ, the opportunity is lost for a one-stage procedure for tumor removal and node sampling. Radiologists should avail themselves of all techniques to minimize histologic underestimation, and that includes using the 11-gauge Mammotome and taking more samples. There is a point of diminishing returns, of course, but Darling et al. [1] haven't reached it yet.
There is no downside to taking a greater number of samples. In my own personal experience of more than 650 11-gauge Mammotome biopsies (and our group's collective experience of 1550 such procedures), we have caused exactly one abscess and zero hematomas requiring surgical intervention. Furthermore, the long-term mammographic evidence of a Mammotome biopsy is minimal and easily recognized [6].
Finally, Darling et al. [1] seem unrepentant in their statement, "In our current practice, no attempt is made to completely mammographically remove a lesion at the time of large-core needle biopsy." Why not? Causing all mammographic evidence of a lesion to disappear has several benefits. First, radiologic-pathologic correlation becomes irrelevant. If, for example, a small nodule with irregular calcifications and indistinct borders is completely removed during a Mammotome biopsy, then a benign fibroadenoma with calcifications is an acceptable diagnosis, regardless of the prebiopsy level of suspicion. Second, short-term follow-up is made easier. At 6 months or 1 year, one does not have to wonder about the adequacy of sampling if the target is gone. By contrast, if the target is visually unchanged at the time of the first follow-up after biopsy, one at least wonders about the adequacy of sampling that was accomplished at the time of the biopsy, particularly if no MicroMark clip (Ethicon Endo-Surgery) was left behind, or if the clip was deployed at some distance from the target. Finally, longterm follow-up is made much easier because an abnormality that ceases to exist cannot be of ongoing concern. For nodules, we no longer face the dilemma of recommending excision of a known benign fibroadenoma that grows after biopsy. For calcifications, leaving none behind means that a subsequent increase from zero to five calcifications will be more easily noticed than a change from 15 to 20.
In summary, there are many reasons to take more than an average of nine samples during an 11-gauge Mammotome biopsy, and Darling et al. [1] explicitly recognize this but seem to have no plans to do so. There are no good reasons not to, because safety has not been an issue. Less is not more in this case, and being timid in stereotactic biopsy serves no one's best interests.
References
Brigham and Women's Hospital Boston, MA 02115
We thank Dr. Guenin for his interest and comments regarding our recently published article, "Atypical Ductal Hyperplasia and Ductal Carcinoma In Situ as Revealed by Large-Core Needle Breast Biopsy: Results of Surgical Excision" [1]. The goal of our investigation was to examine underestimation rates on the basis of our experience of large-core needle breast biopsies with all three of the currently widely used biopsy devices. Our results are consistent with those reported by most authors who have recently published on this topic, as reviewed in the article. For those few cases when markedly lower rates of underestimation were achieved, it is true that more specimens were obtained, on average, by comparison [2,3,4]. However, those authors reporting the lowest underestimation rates (i.e., 0% underestimation) did so with small sample sizes [2, 4]. For both studies reporting the lowest rates of underestimation using the 11-gauge directional vacuum-assisted biopsy device, the range of the number of specimens obtained at the discretion of the radiologist performing the biopsy was widely variable (ranges, 1-34 specimens [3] and 6-34 specimens [4]). Although these investigations imply that more may be better, there is clearly no consensus regarding the optimal number of core specimens, because surgical excision is always indicated after a core biopsy shows atypical ductal hyperplasia, ductal carcinoma in situ, or invasive ductal carcinoma.
Dr. Guenin's second point of discussion addresses the basic philosophy of the minimally invasive biopsy. Percutaneous breast biopsy equipment is approved for the diagnosis of breast cancer, not for its treatment. When faced with a breast abnormality, either calcifications or a mass, the goal of large-core needle biopsy is to sample the lesion as accurately as possible to obtain a pathologic tissue diagnosis that satisfactorily explains the appearance of the lesion. Complete mammographic removal does frequently occur with small lesions, and occasionally complete histologic removal is also accomplished [1]. Sampling is the goal, however, not complete removal. A study cited in our article [4] showed convincingly that even when the goal of the procedure was complete mammographic removal of a lesion using the 11-gauge directional vacuum-assisted biopsy device, residual ductal carcinoma in situ was found at surgical excision 75% of the time and residual invasive carcinoma was found 100% of the time. Presumably, the same principle would be true for benign breast lesions. Furthermore, whether the targeted lesion is completely removed at the time of sampling or not, radiologic—pathologic correlation is always of paramount importance, and decisions about concordance are ultimately the mammographer's responsibility.
We believe that the goal of our investigation was realized on two fronts. First, we confirmed the progressive decrease in underestimation rates in a large series when atypical ductal hyperplasia or ductal carcinoma in situ is revealed by largecore needle breast biopsy using improving technologic devices. In so doing, we justified the advantages of moving to the technically superior 11-gauge directional vacuum-assisted biopsy device, and, at the same time, identified avenues for further improvement. Second, we provided a concise overview of much of the data on underestimation rates for the three most widely used large-core needle biopsy devices, derived from series both large and small. These statistics are useful in enabling patients, surgeons, and radiologists to understand the limitations of the current minimally invasive sampling techniques so that all may develop reasonable expectations with regard to the results of the procedure.
References
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  M F Dillon, C M Quinn, E W McDermott, A O'Doherty, N O'Higgins, and A D K Hill Diagnostic accuracy of core biopsy for ductal carcinoma in situ and its implications for surgical practice. J. Clin. Pathol., July 1, 2006; 59(7): 740 - 743. [Abstract] [Full Text] [PDF]
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