Research Article
Letters
June 2007

Does Size Matter? Likelihood of Cancer in MRI-Detected Lesions Less Than 5 mm

We read the article by Liberman et al. [1] in the February 2006 issue of the AJR with great interest. They assessed the frequency of cancer in MRI-detected breast lesions according to lesion size and found that the likelihood of cancer significantly decreased with decreasing lesion size. In 37 lesions measuring less than 5 mm in size, only one (3%) malignancy was detected that proved to be ductal carcinoma in situ (DCIS). As a consequence, they concluded that biopsy is generally not necessary in breast lesions of less than 5 mm. In addition, they stated that the final decision regarding whether to biopsy a lesion should not be based on lesion size alone but also on patient risk factors, clinical history, and lesion characteristics—that is, morphology and kinetic enhancement curves. In clinical practice, adequate characterization of these small (< 5 mm) breast lesions is essential to reduce the number of unnecessary biopsies in this subgroup of patients.
Unlike Liberman and colleagues, who used analysis of lesion morphology in their study to characterize breast lesions on MRI (kinetic features were only visually assessed), at our institution, we use combined rapid dynamic MRI for quantification of kinetic data and high-spatial-resolution MRI for assessment of breast lesion morphology [2, 3]. Triggered by the results of Liberman et al. we analyzed the data of 27 patients with 30 MRI-detected lesions less than 5 mm in size who underwent MRI-guided needle localization and surgical biopsy at our institution between 1998 and 2005. Indications for MRI of the breast included high-risk screening, suspicious clinical findings, indeterminate findings on conventional imaging, and staging of known breast cancer. Analysis of lesion morphology according to the BI-RADS–MRI lexicon criteria [4] revealed oval smooth margins (n = 12), round smooth margins (n = 11), irregular margins (n = 5), spiculated margins (n = 1), and lobulated margins (n =1).
Kinetic enhancement curves of the 30 lesions were coded as benign (gradual wash-in of contrast material) in seven, indeterminate (wash-in of contrast material followed by plateau phase) in 10, and suspicious (wash-in followed by wash-out of contrast material) in 11; in two lesions, the curve analysis was not possible because of the small size. Lesion size varied from 2 to 4 mm. Histopathologic analysis showed 11 (37%) of the 30 lesions to be malignancies (three invasive ductal carcinomas, three invasive lobular carcinomas, one tubular carcinoma, and four DCIS). Three (10%) of the 30 were high-risk lesions, and 16 (53%) of the 30 were benign lesions.
In our study [3], the overall percentage of malignancies in the group of MRI-detected breast lesions less than 5 mm was 37%, which is considerably higher than the 3% reported by Liberman et al. [1]. Most lesions presented as a round or oval mass with smooth margins, and no morphologic features significantly differentiated between benign and malignant small breast lesions. On the other hand, all 11 malignancies presented with abnormal enhancement kinetics, either classified as indeterminate (n = 4) or suspicious (n = 7) (p < 0.05). These findings stress the importance of kinetic enhancement curve analysis, especially when evaluating small (< 5 mm) breast lesions on MRI.

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References

1.
Liberman L, Mason G, Morris EA, Dershaw DD. Does size matter? Positive predictive value of MRI-detected breast lesions as a function of lesion size. AJR 2006; 186:426–430
2.
Agoston AT, Daniel BL, Herfkens RJ, et al. Intensity-modulated parametric mapping for simultaneous display of rapid dynamic and high-spatial-resolution breast MR imaging data. RadioGraphics 2001; 21:217–226
3.
Van den Bosch MAAJ, Daniel BL, Pals S, et al. MRI-guided needle localization of suspicious breast lesions: results of a freehand technique. Eur Radiol 2006; 16:1811 –1817
4.
Ikeda DM, Hylton NM, Morris EA, et al. Illustrated breast imaging reporting and data system: magnetic resonance imaging (BI-RADS–MRI). Reston, VA: American College Of Radiology,2003

Information & Authors

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Published In

American Journal of Roentgenology
Pages: W571
PubMed: 17515352

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Affiliations

Maurice A. A. J. Van den Bosch
Stanford University Medical Center Stanford, CA
Debra M. Ikeda
Stanford University Medical Center Stanford, CA
Bruce L. Daniel
Stanford University Medical Center Stanford, CA

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