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Original Research |
1 Department of Mammography, Institute of Diagnostic and Interventional
Radiology, Friedrich Schiller University, Bachstrasse 18, Jena D-07740,
Germany.
2 Institute of Pathology, Friedrich Schiller University, Ziegelmühlenweg,
Jena, Germany.
3 Department of Gynaecology, Friedrich Schiller University, Jena, Germany.
4 Present address: Department of Gynaecology, Charité
Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin,
Germany.
Received October 27, 2004;
accepted after revision November 23, 2004.
Address correspondence to S. Wurdinger
(Susanne.Wurdinger{at}med.uni-jena.de).
Abstract
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MATERIALS AND METHODS. MR images were obtained on a 1.5-T imager. T1- and T2-weighted sequences and dynamic 2D fast-field echo T1-weighted sequences were performed. MR images of 23 patients with 24 phyllodes breast tumors (one malignant, 23 benign) were analyzed with respect to morphology and contrast enhancement. The tumors were compared with the MRI appearance of 81 fibroadenomas of 75 patients.
RESULTS. Well-defined margins were seen in 87.5% of the phyllodes tumors and 70.4% of the fibroadenomas, and a round or lobulated shape in 100% and 90.1%, repectively. A heterogeneous internal structure was observed in 70.8% of phyllodes tumors and in 49.4% of fibroadenomas. Nonenhancing internal septations were found in 45.8% of phyllodes tumors and 27.2% of fibroadenomas. A significantly greater increase in signal was seen on T2-weighted images in the tissue surrounding phyllodes tumors (21%) compared with fibroadenomas (1.2%). Most of both lesions appeared with low signal intensity on T1- and T2-weighted images. After the administration of contrast material, 33.3% of phyllodes tumors and 22.2% of fibroadenomas showed a suspicious signal intensity-time course.
CONCLUSION. Phyllodes breast tumors and other fibroadenomas cannot be precisely differentiated on breast MRI. Phyllodes tumors have benign morphologic features and contrast enhancement characteristics suggestive of malignancy in 33% of cases.
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The appearance of these breast tumors, especially small lesions, on sonography and mammography usually does not allow the distinction of a fibroadenoma and a phyllodes breast tumor that needs therapy. Therefore, the possibility of differentiation and specification of phyllodes breast tumors on dynamic breast MRI was evaluated.
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MR images were obtained on a 1.5-T imager (Gyroscan ACS II, Philips Medical Systems) using a dedicated double breast coil. All patients were examined in the prone position using an identical protocol. Before imaging, saline was injected IV into a cubital vein.
After an initial scout image was obtained, a T1-weighted fast-field echo sequence was obtained in the coronal or axial orientation. For the dynamic study, 2D multislice images were obtained using a fast-field echo T1-weighted sequence with the following parameters: TR/TE, 97/5.0; flip angle, 80°; slice thickness, 4.0 mm; gap, 0.4 mm; field of view, 315 x 350 mm2; matrix, 230 x 256 (90% rectangular field of view) corresponding to an in-plane scan resolution of 1.37 x 1.37 mm; axial orientation; 24 slices covering both breasts. After acquisition of a native scan, gadopentetate dimeglumine (0.1 mmol/kg of body weight, Magnevist, Schering) was administered IV as a rapid bolus within 10 sec followed by a 20-mL saline flush. After bolus and saline administration, dynamic scanning was continued with the same sequence parameters and under identical tuning conditions at 1-min intervals for a total of 8 min. After the dynamic scanning, the first coronal or axial T1-weighted scanning was repeated approximately 10 min after contrast administration, followed by axial T2-weighted turbo spin-echo imaging in identical slice positions. Post-processing of the dynamic study included calculation of time-signal intensity curves and subtraction of unenhanced images from the contrast-enhanced dynamic images.
Lesions exclusively seen on MR and lesions that were not reliably located compared with the findings of mammography or sonography were marked under MR guidance using an MR-compatible double-breast device and titanium wires (MR eye needle, Cook).
MR images were evaluated retrospectively and in consensus by two residents and one experienced radiologist. Breast lesions were described without knowledge of the histopathologic results. The following data were recorded: margins (smooth, irregular), shape (round, lobulated, irregular), internal structure (homogeneous, heterogeneous, internal septations), signal intensity of the lesion and the surrounding tissue on T2-weighted images (compared with tissue of the breast), signal intensity of the lesion on T1-weighted images, and contrast enhancement characteristics with signal intensity course after contrast administration (slow initial contrast enhancement with persistent delayed phase, fast initial contrast enhancement with plateau phase, fast initial contrast enhancement with wash-out phenomenon).
Comparison of the data in the group with phyllodes breast tumors and the group with other fibroadenomas was performed using Fisher's exact test, with the level of significance set at p < 0.05.
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Tumor sizes of the benign phyllodes breast tumors ranged from 9 to 50 mm (average size, 23 mm). The malignant tumor was 75 mm. Five tumors were smaller than 10 mm, 11 tumors were between 10 and 20 mm, and eight tumors were larger than 20 mm. The size of fibroadenomas ranged from 3 to 70 mm (average, 19 mm). There were 22 fibroadenomas smaller than 10 mm, 38 fibroadenomas between 10 and 20 mm, and 21 tumors larger than 20 mm.
Morphology
Most phyllodes breast tumors had smooth margins (87.5%, n = 21),
were round or lobulated (100%, n = 24), and had a heterogeneous
internal structure (70.8%, n = 17); 11 lesions (45.8%) showed
nonenhancing septations.
The morphologic features of fibroadenomas were similar: 70.4% (n = 57) had smooth margins and 90.1% (n = 73) were round or lobulated. Lesions with a heterogeneous internal structure or nonenhancing septations were less frequent among the group of fibroadenomas, 49.4% (n = 40) and 27.2% (n = 22), respectively. Further details are shown in Table 1 and the findings of the malignant tumor are represented in Figures 1A, 1B, 1C, 1D, and 1E.
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Signal Intensity
The phyllodes breast tumors and fibroadenomas were hypointense or
isointense lesions compared with adjacent breast tissue on T1-weighted images
(Table 2). On T2-weighted
images, eight (33.3%) of 24 phyllodes tumors and 27 (33.3%) of 81
fibroadenomas had a hyperintense signal. Sixteen phyllodes breast tumors were
hypointense, and three of these showed bright cystic areas inside the tumor.
Fifty-four fibroadenomas (66.7%) had a similar hypointense signal intensity,
with three of the 54 being cystic tumors. The surrounding tissue or the whole
tumor-yielding breast had high signal intensity on T2-weighted images in five
of 24 phyllodes breast tumors and in one of 81 fibroadenomas.
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Contrast Enhancement Characteristics
Three types of contrast medium enhancement patterns were differentiated:
the type 1 enhancement pattern indicated benign lesions, and types 2 and 3
patterns were suggestive of malignancy
[5-7].
In the type 1 pattern, 16 (66.7%) of 24 phyllodes breast tumors and 63 (77.8%)
of 81 fibroadenomas were classified as lesions with slow initial contrast
enhancement and a persistent delayed phase, indicating benign lesions. The
type 2 contrast enhancement pattern, with fast initial and plateau phases, was
seen in three phyllodes tumors (12.5%) and eight fibroadenomas (9.9%). Five
phyllodes tumors (20.8%) and 10 fibroadenomas (12.3%) were classified as the
type 3 pattern of contrast enhancement, with a fast initial phase and a
wash-out phenomenon.
Statistical Analysis
Morphologic features, the signal intensity of tumors and surrounding
tissue, and the contrast enhancement characteristics of phyllodes breast
tumors and fibroadenomas were compared. Only one significant difference was
seen between these two types of breast tumors: high signal intensity on
T2-weighted images of surrounding breast tissue (p = 0.005) (i.e., a
surrounding liquid accumulation) occurred significantly more often in
phyllodes breast tumors than in fibroadenomas.
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In our study, the prevalence of phyllodes breast tumors is higher (3%) than in other studies (0.3-1%) [1, 2]. Phyllodes tumors become conspicuous as a result of their rapid growth, and usually they do not have typical benign calcifications [10]. Particularly in small phyllodes tumors, an overlap with breast cancer exists. Patients in this study had been referred to our gynecology department for clarification of the nature of suspicious breast lesions. Possibly, the choice of a preselected study population with a high prevalence of disease influenced the prevalence of phyllodes breast tumors in our cohort.
The number of phyllodes breast tumors reported on MRI is limited. Well-defined margins with a round or lobulated shape and a septate inner structure have been described as characteristic morphologic signs [11-13]. Most tumors in our study showed well-defined margins. However, three tumors with blurred margins were seen. Liberman et al. [14] described one of 12 phyllodes tumors as having ill-defined margins, whereas Buchberger et al. [15] showed exclusively phyllodes tumors with smooth margins on breast sonography. The small size of the tumors with ill-defined margins (< 20 mm) and the use of hard-copy images might have influenced the assessment of the margins. In our study, fibroadenomas showed a similar high percentage with smooth margins and a round or lobulated shape. Other breast MRI studies confirm smooth margins and round or lobulated shape in most fibroadenomas [16].
Although the percentage of shape and margins did not really provide a distinction, we found a nonsignificant difference in heterogeneous inner structure and nonenhancing septation, with 70.8% and 49.4%, respectively, for phyllodes breast tumors and with 49% and 27.2% for fibroadenomas. Inner septations have been found in fibroadenomas in up to 40% of cases [16]. They were defined as typical signs of fibroadenomas. However, several studies have shown inner septations also as a morphologic sign of phyllodes breast tumors [12, 13, 17]. Heterogeneous inner structure may be caused by regressive changes during tumor growth. Possibly, phyllodes tumors have such architecture more frequently because of their rapid growth. We also found a higher percentage of heterogeneous tumors in the phyllodes group. Chao et al. [18] had similar results in a sonographic study. They concluded that a phyllodes tumor should be considered when a round or lobulated tumor shows a heterogeneous inner structure.
Signal intensity on T2-weighted images was high in one third of tumors in both groups. Study data by Kuhl et al. [19] showed high signal intensity on T2-weighted images in 62-76% of fibroadenomas. The difference of one third might be explained by the different kind of imaging and contrast administration. Although those authors administered the contrast medium after acquiring the T2-weighted images, the T2-effect of the contrast medium by imaging after contrast administration may have influenced our evaluation and caused a decrease in the percentage of bright lesions. Another reason for the difference in our findings could be the different study populations; the study by Kuhl et al. had a higher percentage of young women with "younger" nonsclerotic fibroadenomas.
Some case studies have described cysts and hemorrhage as typical signs of phyllodes breast tumors [11-13, 17]. More than 50% of the phyllodes tumors in our study did not show any bright area on T2-weighted images, and hemorrhage was associated with cystosarcomas exclusively, which was confirmed by our pathologist. In the mentioned studies, only large tumors were analyzed, whereas in our study two thirds of phyllodes tumors were smaller than 20 mm. Cysts and hemorrhage are supposed to be an effect of rapid growth and size, with regressive changes occurring in large tumors.
Two patients with phyllodes tumors and six patients with fibroadenomas had symmetric bilateral areas of high signal intensity (edema) on T2-weighted images occurring during hormonal changes. In contrast, five of 24 phyllodes tumors and one of 81 fibroadenomas showed surrounding unilateral edema. All were larger than 20 mm. Grebe et al. [11] also found edema surrounding a large phyllodes tumor. The interstitial edema of tissue was interpreted as a liquid collection in rapidly growing tumors in compressed mammary ducts or lymph vessels. The contrast medium enhancement patterns of malignant breast lesions with a rapid wash-in and plateau or wash-out phenomenon (types 2 and 3) in dynamic imaging have been described by several authors [5-7, 20]. But there is also an overlap of contrast enhancement patterns between breast cancer and benign breast lesions.
Previous studies described up to 9% of slowly enhancing invasive breast tumors (type 1) and up to 18% of suspicious enhancing benign lesions (types 2 and 3) [6, 7, 21]. One third of phyllodes breast tumors and 23% of fibroadenomas in our study showed a typical malignant pattern of contrast enhancement. This finding is restricted to visual analysis of film prints, and differences might be explained by this fact. Also, the study population of patients who underwent surgery because of suspicious tumors on mammography, sonography, or breast MRI could have influenced the higher percentage of rapidly enhancing breast lesions. Kinoshita et al. [17] also showed benign and malignant enhancement patterns in eight phyllodes tumors. Case studies confirm the suspicious contrast enhancement of large phyllodes tumors [12, 13, 20]. Buadu et al. [20] supposed a different contrast enhancement pattern for a cystosarcoma phyllodes tumor and three benign phyllodes tumors. However, in our study no difference could be found between one cystosarcoma phyllodes and seven suspicious enhancing benign phyllodes tumors.
Large phyllodes breast tumors may have a typical morphology with smooth margins, internal cysts, septations, and hemorrhage or perifocal or unilateral edema (Figs. 1A, 1B, 1C, 1D, and 1E), but a reliable differentiation of phyllodes tumors and fibroadenomas was not possible in our study. Phyllodes breast tumors and fibroadenomas may have a contrast enhancement pattern suggestive of malignancy in up to one third of cases, and some probably benign lesions cannot be differentiated from breast cancer, especially from mucinous carcinoma, on breast MRI.
Acknowledgments
We thank Ines Krumbein for assistance with the images.
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