(Radiology. 2000;214:67-72.)
© RSNA, 2000
Evaluation of Pectoralis Major Muscle in Patients with Posterior Breast Tumors on Breast MR Images: Early Experience1
Elizabeth A. Morris, MD,
Lawrence H. Schwartz, MD,
Michele B. Drotman, MD,
Su J. Kim, MD,
Lee K. Tan, MD,
Laura Liberman, MD,
Andrea F. Abramson, MD,
Kimberly J. Van Zee, MD and
D. David Dershaw, MD
1 From the Departments of Radiology (E.A.M., L.H.S., M.B.D., S.J.K., L.L., A.F.A., D.D.D.), Pathology (L.K.T.), and Surgery (K.J.V.Z.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021. Received March 5, 1998; revision requested April 29, 1998; revision received April 29, 1999; accepted June 15. Address reprint requests to E.A.M. (e-mail: morrise@mskcc.org).
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Abstract
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PURPOSE: To evaluate the ability to use breast magnetic resonance (MR) imaging to assess disease extent in patients with posterior breast masses who are suspected to have tumor invasion into underlying muscle.
MATERIALS AND METHODS: Nineteen patients with posterior breast masses underwent three-dimensional, gradient-echo, 1.5-T MR imaging before and after the administration of gadopentetate dimeglumine. Thirteen had deep palpable masses that were clinically determined to be fixed to the underlying chest wall. Twelve had mammographic findings that caused muscle involvement to be suspected, and seven had normal mammograms. All patients underwent surgery. MR images were reviewed and were correlated with histologic findings.
RESULTS: Enhancing masses were identified on MR images in all 19 patients. Five (26%) of the 19 patients had masses that abutted the muscles, with obliteration of the fat plane and muscle enhancement. All five had muscle involvement at surgery. In the remaining 14 (74%) patients, no enhancement of muscle was seen; none of these had invasion of the muscle at surgery.
CONCLUSION: Extension of adjacent tumor into underlying musculature was indicated by abnormal enhancement within these structures. Violation of the fat plane between tumor and muscle, without other findings, did not indicate tumor involvement of these deep structures.
Index terms: Breast neoplasms, diagnosis, 00.30 • Breast neoplasms, MR, 00.121412, 00.121413, 00.121415, 00.12143 • Breast neoplasms, staging, 00.30 • Magnetic resonance (MR), contrast enhancement, 00.12143
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Introduction
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Masses that are located in the posterior aspect of the breast can be difficult to evaluate with mammography and physical examination. Mammography may only partially depict the posterior breast mass, if it does so at all (1,2). Assessment with mammography can be especially compromised if the breast is dense or the mass is fixed to the underlying muscle. Physical examination is even less sensitive than mammography and has been shown to result in underestimation of the extent of disease, with clinical measurements of tumor size that often are inaccurate and with substantial variation among clinicians performing breast examinations (3).
Assessment of the extent of disease can also be problematic with large tumors, despite their being easily palpable. Margins of locally advanced breast cancers can be difficult to determine if they manifest as diffuse infiltration without a dominant mass. Moreover, peritumoral inflammation can mimic tumoral infiltration, which results in overestimation of the extent of disease (4) at mammography and at physical examination.
Assessment of disease extent is important for surgical planning, staging for prognosis, and consideration for preoperative chemotherapy. Optimal surgical results rely on the ability to obtain clear histologic margins, as this is an important predictor of local control (5,6). Accurate assessment of tumor size and extension aids the surgeon in obtaining clear margins and decreases the number of repeat operations and the chance of local recurrence.
In posterior lesions, especially in those close to the chest wall musculature, this information may not be available from conventional diagnostic studies, such as mammography, prior to surgery. If tumor extends to and superficially invades the pectoralis major muscle, a portion of the muscle will be removed to obtain a negative posterior margin (7). If a large portion of the underlying pectoralis major muscle is involved, radical mastectomy may be necessary. If the tumor extends to involve the chest wall (ribs, intercostal muscles, serratus anterior muscle), the patient may require preoperative chemotherapy and/or radiation therapy and possible chest wall resection for treatment (7). Thus, it is critical to map the extent of disease so that the appropriate management is planned.
Previous authors have shown that breast magnetic resonance (MR) imaging is more sensitive than mammography in the detection of tumor (4,8–10) and is superior to physical examination and mammography in the assessment of the extent of disease (11). This study was undertaken to examine if MR imaging of the breast could reliably be used to determine the extension of posterior breast masses when invasion of underlying musculature was suspected at mammography or physical examination.
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MATERIALS AND METHODS
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For 4 years from June 1994 to November 1998, preoperative MR imaging was prospectively performed in 19 women, with 19 masses in the posterior third of the breast, who were suspected to have pectoralis major muscle involvement at mammography or physical examination. Women ranged in age from 23 to 64 years (mean age, 46 years). Thirteen breast masses were in the left breast, and six were in the right breast. Twelve were in the upper outer quadrant, five were in the upper inner quadrant, and two were in the lower outer quadrant. The mean mass size was 3 cm (range, 1.3–6.0 cm).
Of the 19 masses, 13 were palpable. All of these were determined to be fixed to the chest wall at physical examination by a breast surgeon. Breast density at mammography was as follows: dense in five cases, heterogeneously dense in eight cases, scattered fibroglandular densities in four cases, and fatty in two cases. Twelve of the 19 masses were seen on the mammograms. Ten masses were inseparable from the muscle on the mammograms; two masses were incompletely depicted, and the muscle attachment could not be assessed. At mammography, seven masses were not identified. All of these were in dense (n = 5) or heterogeneously dense (n = 2) breasts. One of these masses was also located at the inframammary fold, and the site could not be imaged at mammography.
Histopathologic diagnoses of the masses were 14 infiltrating ductal carcinomas, one infiltrating lobular carcinoma, one ductal carcinoma in situ, one fibromatosis, one fibroadenoma, and one spindle cell sarcoma.
Prior breast surgery had been performed in four patients for the following reasons: ipsilateral invasive ductal carcinoma in two patients, ipsilateral malignant phyllodes tumor in one patient, and contralateral benign phyllodes tumor in one patient.
At 0–5 weeks (mean, 2 weeks) before the MR examination, all patients underwent mammography at a Mammography Quality Standards Act–certified mammography facility either with a model M-III (Lorad, Danbury, Conn) or a model 600T or DMR (GE Medical Systems, Milwaukee, Wis) mammography system. All mammograms were reviewed by a mammographer (E.A.M.) prior to MR imaging.
All patients gave informed consent. MR imaging was performed with a 1.5-T commercially available system (Signa; GE Medical Systems). Patients were imaged in the prone position by using a dedicated surface breast coil.
The MR imaging protocol was performed with one of two sequences. Before June 1997, 11 examinations were performed with a three-dimensional, fast, multiplanar, spoiled gradient-recalled-echo (19.7/1.7 [repetition time msec/echo time msec]; flip angle, 30°) sequence, with which the images were obtained sagittally by using chemical fat suppression, for an acquisition time per series of 5–10 minutes. The subsequent eight examinations were performed with a three-dimensional, fast spoiled gradient-recalled-echo (9/4.2/30 [repetition time msec/echo time msec/inversion time msec]; flip angle, 10°) sequence, where the images were obtained sagittally by using a spectral inversion-recovery sequence, for an acquisition time per series between 1 minute 53 seconds and 4 minutes.
A section thickness between 1.8 and 2.5 mm (mean, 2 mm), without a gap, and with a 256 x 192 matrix and a 16–18-cm field of view was used in both protocols. Images were obtained prior to and following the administration of 0.1 mmol/L gadopentetate dimeglumine (Magnevist; Berlex, Wayne, NJ) per kilogram of body weight. Contrast material was administered as a rapid bolus injection through an indwelling intravenous catheter. Static image acquisition started immediately following contrast material injection. Subtraction of the precontrast images from the postcontrast images was performed on a pixel-by-pixel basis by using an Advantage Windows workstation (GE Medical Systems).
Breast MR images were interpreted by two radiologists in consensus (E.A.M., L.H.S.). All enhancing lesions were measured. If the mass did not extend to the muscle, the distance from the muscle was measured. If the mass extended to the muscle, completely violating the fat plane, the presence of enhancement within the muscle was noted. Overall configuration of the muscles was evaluated for mass effect.
After gadopentetate dimeglumine administration, muscle will normally demonstrate some enhancement. To ensure that normal muscle enhancement was not mistaken for tumor enhancement, the relative signal intensities of the muscle before and after contrast material enhancement were measured for all cases. Signal intensity readings were taken of the muscle at the point closest to the mass in all cases. A region of interest of 10 mm2 was used, which was placed manually over the area of the muscle with the highest signal intensity. A total of three signal intensity unit readings were obtained before and after contrast material administration by evaluating three contiguous sections. A mean signal intensity measurement was then assigned to the muscle in each case. To standardize the signal intensity calculation, the following formula was used: (SICE - SInonCE)/noise, where noise is the SD of background fat, SICE is the contrast-enhanced signal intensity of muscle, and SInonCE is the nonenhanced signal intensity of muscle; this helped us avoid the problems inherent in measuring noise outside of the breast coil (12).
All patients underwent surgery, and MR imaging findings were correlated with histologic findings. A single pathologist (L.K.T.) reviewed all the cases, evaluated the breast mass, and specifically sought evidence of extension into muscle. Eleven patients underwent lumpectomy, six underwent modified radical mastectomy, one underwent radical mastectomy, and one underwent partial chest wall resection.
We used the Fischer exact test. A P value less than .05 was considered to indicate a significant difference.
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RESULTS
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Enhancing masses were present in all 19 patients on breast MR images. Morphologic assessment of the masses was classified in accordance with Breast Imaging Reporting and Data System, or BI-RADS, terminology and enhancement characteristics (13). At MR examination, nine patients had masses that were irregular and spiculated, with heterogeneous enhancement; three, irregular and ill defined, with heterogeneous enhancement; three, lobular and circumscribed, with heterogeneous enhancement; one, round and circumscribed, with rim enhancement; and three, multiple spiculated and indistinct masses with heterogeneous enhancement. These last three patients had additional foci of cancer that were not suspected at physical examination or mammography.
Histologic analysis showed pectoralis major muscle invasion in five (26%) of 19 masses. Correlation between MR imaging and histologic findings is shown in Table 1. Pectoralis major muscle invasion was present in five (100%) of the five masses that showed pectoralis major muscle enhancement versus none (0%) of the 14 masses without associated pectoralis major muscle enhancement (P < .001).
Five patients had masses that extended to the muscle, which obliterated the fat plane, and had associated enhancement of the underlying pectoralis major muscle (Fig 1). All of these had muscle invasion at surgery. Of these five patients, three had a prior history of breast tumor; the histologic diagnoses of the recurrent masses were infiltrating ductal carcinoma in two patients and spindle cell sarcoma in one. In all three patients with recurrent tumor, multiple masses in the breast were identified, and the tumor was noted to extend through the full thickness of the pectoralis major muscle or into the chest wall. Both of the patients without recurrent disease and with pectoralis major muscle enhancement had locally advanced breast cancer at presentation. In both, the masses were large infiltrating ductal carcinomas, measuring 5 and 6 cm, that were found at histologic analysis to have invaded the pectoralis major muscle.
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Figure 1a. Recurrent infiltrating ductal carcinoma treated with radical mastectomy in a 45-year-old woman. Sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo (a) precontrast and (b) postcontrast MR images (19.7/1.7; flip angle, 30°). In b, the mass (m) obliterates the fat plane (long straight solid arrow), and there is enhancement of the underlying pectoralis major muscle (p and short straight solid arrows). At surgery, the full thickness of the pectoralis major muscle was involved with tumor. Additional areas of recurrent disease are noted inferiorly (curved arrow in b). Enhancement within the thickened skin (open arrow in b) proved to represent tumor invasion.
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Figure 1b. Recurrent infiltrating ductal carcinoma treated with radical mastectomy in a 45-year-old woman. Sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo (a) precontrast and (b) postcontrast MR images (19.7/1.7; flip angle, 30°). In b, the mass (m) obliterates the fat plane (long straight solid arrow), and there is enhancement of the underlying pectoralis major muscle (p and short straight solid arrows). At surgery, the full thickness of the pectoralis major muscle was involved with tumor. Additional areas of recurrent disease are noted inferiorly (curved arrow in b). Enhancement within the thickened skin (open arrow in b) proved to represent tumor invasion.
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In the five patients with pectoralis major muscle enhancement, two patterns of enhancement were seen. Four of five patients had a diffuse infiltrative enhancement pattern without mass effect and with preservation of muscular architecture (Fig 2). All of these patients had direct tumor extension into muscle at surgery. One patient had a masslike enhancement that expanded the pectoralis major muscle, with loss of the normal muscle striations (Fig 1). This patient had penetration of the chest wall (intercostal and serratus muscles) by tumor.
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Figure 2a. Locally advanced breast cancer in a 53-year-old woman. At physical examination, there was a 6-cm mass (m in b) fixed to the chest wall at palpation; that is, the mass was immobile at physical examination. Performing an adequate mammographic examination was compromised by the large size of the mass and the firmness of the breast. (a, b) Sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo (a) precontrast and (b) postcontrast MR images (19.7/1.7; flip angle, 30°). b demonstrates full-thickness involvement of the inferior aspect of the pectoralis major muscle (p and straight arrows). Obliteration of the fat plane (curved arrow in b) is identified. (c) Photomicrograph of pathologic specimen reveals infiltrating lobular cancer. The breast mass obliterates the fat plane (large arrow), and tumor cells (small arrows) invade the pectoralis major muscle. (Hematoxylin-eosin stain; original magnification, x20.)
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Figure 2b. Locally advanced breast cancer in a 53-year-old woman. At physical examination, there was a 6-cm mass (m in b) fixed to the chest wall at palpation; that is, the mass was immobile at physical examination. Performing an adequate mammographic examination was compromised by the large size of the mass and the firmness of the breast. (a, b) Sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo (a) precontrast and (b) postcontrast MR images (19.7/1.7; flip angle, 30°). b demonstrates full-thickness involvement of the inferior aspect of the pectoralis major muscle (p and straight arrows). Obliteration of the fat plane (curved arrow in b) is identified. (c) Photomicrograph of pathologic specimen reveals infiltrating lobular cancer. The breast mass obliterates the fat plane (large arrow), and tumor cells (small arrows) invade the pectoralis major muscle. (Hematoxylin-eosin stain; original magnification, x20.)
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Figure 2c. Locally advanced breast cancer in a 53-year-old woman. At physical examination, there was a 6-cm mass (m in b) fixed to the chest wall at palpation; that is, the mass was immobile at physical examination. Performing an adequate mammographic examination was compromised by the large size of the mass and the firmness of the breast. (a, b) Sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo (a) precontrast and (b) postcontrast MR images (19.7/1.7; flip angle, 30°). b demonstrates full-thickness involvement of the inferior aspect of the pectoralis major muscle (p and straight arrows). Obliteration of the fat plane (curved arrow in b) is identified. (c) Photomicrograph of pathologic specimen reveals infiltrating lobular cancer. The breast mass obliterates the fat plane (large arrow), and tumor cells (small arrows) invade the pectoralis major muscle. (Hematoxylin-eosin stain; original magnification, x20.)
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In six patients (32%), breast masses abutted the pectoralis major muscle, obliterating the intervening fat plane, but did not demonstrate muscle enhancement above the baseline pattern (Fig 3). None of these patients had tumor involvement of muscle at surgery.
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Figure 3a. Extremely mammographically dense breast and axillary lymph nodes sampled by using fine-needle aspiration, which demonstrated an adenocarcinoma that was suspected to be the primary cancer, in a 46-year-old woman. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo MR images (19.7/1.7; flip angle, 30°). Physical examination and mammographic findings were negative. b shows a posterior mass (m) that obliterates a fat plane (arrow), with no underlying enhancement of the pectoralis major muscle (p). Histopathologic analysis yielded a 1.3-cm infiltrating ductal carcinoma without extension into the underlying muscle.
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Figure 3b. Extremely mammographically dense breast and axillary lymph nodes sampled by using fine-needle aspiration, which demonstrated an adenocarcinoma that was suspected to be the primary cancer, in a 46-year-old woman. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo MR images (19.7/1.7; flip angle, 30°). Physical examination and mammographic findings were negative. b shows a posterior mass (m) that obliterates a fat plane (arrow), with no underlying enhancement of the pectoralis major muscle (p). Histopathologic analysis yielded a 1.3-cm infiltrating ductal carcinoma without extension into the underlying muscle.
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Eight (42%) of 19 patients had masses that were close to the chest wall but did not completely obliterate the fat plane and therefore did not directly contact the underlying muscle, according to MR criteria. The mean distance between the mass and the muscle wall in these patients was 0.5 cm (range, 0.2–1.1 cm). Five of these had radiating, contrast-enhancing spiculations that extended toward the pectoralis major muscle, with the presence of intervening fat (Fig 4). The remaining three had a smooth fat plane between the posterior margin of the mass and the underlying muscle, without the presence of spiculations (Fig 5). None of these patients had tumor involvement of the underlying muscle at surgery.
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Figure 4a. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-echo MR images (19.7/1.7; flip angle, 30°) obtained in a 59-year-old woman with a 2.5-cm mass fixed to the chest wall at palpation (ie, the mass was immobile at physical examination) who had overlying skin thickening at physical examination. The patient underwent breast MR imaging because of concern of fixation to the chest wall. b demonstrates a spiculated mass (m) that involves the skin (short arrows). The spiculations (long arrow in b) extend from the mass to the underlying pectoralis major muscle (p in b). No abnormal enhancement of the muscle is identified. Histopathologic analysis yielded infiltrating ductal carcinoma without muscle involvement. The presence of spiculations alone was not indicative of involvement.
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Figure 4b. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-echo MR images (19.7/1.7; flip angle, 30°) obtained in a 59-year-old woman with a 2.5-cm mass fixed to the chest wall at palpation (ie, the mass was immobile at physical examination) who had overlying skin thickening at physical examination. The patient underwent breast MR imaging because of concern of fixation to the chest wall. b demonstrates a spiculated mass (m) that involves the skin (short arrows). The spiculations (long arrow in b) extend from the mass to the underlying pectoralis major muscle (p in b). No abnormal enhancement of the muscle is identified. Histopathologic analysis yielded infiltrating ductal carcinoma without muscle involvement. The presence of spiculations alone was not indicative of involvement.
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Figure 5a. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo MR images (19.7/1.7; flip angle, 30°) obtained in a 23-year-old woman with a history of contralateral cystosarcoma phyllodes tumor. A routine CT scan demonstrated a questionable mass in the posterior aspect of the breast that was not appreciated at physical examination or mammography. b demonstrates a 1.5-cm mass (m) in the posterior part of the breast, with a smooth fat plane ( f ) between the posterior margin of the mass and the underlying muscle (p). Histopathologic analysis yielded fibroadenoma.
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Figure 5b. (a) Precontrast and (b) postcontrast sagittal, fat-suppressed, three-dimensional, fast multiplanar spoiled gradient-recalled-echo MR images (19.7/1.7; flip angle, 30°) obtained in a 23-year-old woman with a history of contralateral cystosarcoma phyllodes tumor. A routine CT scan demonstrated a questionable mass in the posterior aspect of the breast that was not appreciated at physical examination or mammography. b demonstrates a 1.5-cm mass (m) in the posterior part of the breast, with a smooth fat plane ( f ) between the posterior margin of the mass and the underlying muscle (p). Histopathologic analysis yielded fibroadenoma.
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Table 2 demonstrates the mean increase in the signal-to-noise ratio in cases with and in cases without muscle invasion. The increase in the signal-to-noise ratio in those cases without invasion was due to normal enhancement after contrast material administration. In all cases of muscle invasion, the degree of enhancement of the underlying muscle was greater than the expected baseline enhancement (P = .001). The enhancement that caused tumor invasion to be suspected was readily apparent to both observers, without signal intensity measurements.
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DISCUSSION
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Breast cancer treatment is based on the accurate assessment of the stage and extent of disease. Breast MR imaging is extremely sensitive in the detection of breast cancer (4,8,9) and has numerous advantages over mammography, including improved anatomic detail, imaging in multiple planes, and the ability to image the chest wall (10). These advantages are especially important when assessing posterior breast lesions that may involve the underlying muscle. Because of superior anatomic representation, MR imaging is able to allow differentiation of the various muscles of the chest and can be used to assess whether the tumor involves only the pectoralis major muscles or involves the serratus and intercostal muscles (chest wall).
This distinction is important for both staging and treatment planning. The patient with tumor extension into the chest wall (stage T4 according to TNM classification) is considered stage IIIB, with an associated grave prognosis, whereas invasion of the pectoralis major muscle alone by tumor does not affect staging (14). Invasion of the pectoralis major muscle may require muscle resection at the time of surgery, while chest wall invasion may require chest wall resection. Therefore, accurate assessment of tumor involvement has important implications for treatment planning. In addition, owing to the use of intravenous contrast material, which helps map the tumor vascularity, breast MR imaging is helpful in outlining tumor extent, especially when the tumor infiltrates adjacent muscle without producing an obvious mass effect.
Among our patients, MR imaging was useful in predicting the extent of local tumor involvement and thereby helped guide surgical planning. In one patient, extensive involvement of the full thickness of the pectoralis major muscle confirmed the need for radical mastectomy. Less extensive involvement of the full thickness of the pectoralis major muscle would have made possible either lumpectomy with removal of the involved portion of the muscle or modified radical mastectomy. Findings of more extensive chest wall involvement resulted in the guidance of therapy away from these options toward chest wall resection.
In women with palpable cancers obscured by dense tissue at mammography, MR was useful in mapping the extent of local disease. In seven women with negative mammograms, all had masses identified on breast MR images. In four patients with recurrent tumor after breast conservation, MR imaging was more accurate than mammography in the identification of local disease extent. As mammography is compromised in women who have previously undergone breast-conservation therapy (15), the greater accuracy of MR imaging in this setting is not surprising.
In all cases, muscle enhancement due to tumor involvement was easily distinguished from the baseline enhancement that occurs within the pectoralis major muscle following contrast material injection. On contrast-enhanced MR images, there is a normal pattern of enhancement of the vascular pectoralis major muscle and its vessels. Normal vessels were readily distinguishable from the tumor enhancement, as they were smooth, demonstrated branching, and were able to be followed over sequential sagittal images.
Table 2 demonstrates that tumor enhancement of the muscle was significantly different (P = .001) from the baseline level of enhancement. Table 2 also shows that there is variation in the baseline enhancement, which likely is due to the heterogeneity of muscle tissue. The two types of muscle enhancement were quantitatively different (Table 2), although there was overlap between baseline enhancement and tumor enhancement. Although the numbers in this study are small, separation of the two types of enhancement could not be made with quantitative data alone with 100% confidence. Tumor enhancement of muscle was visible to the observer in a qualitative fashion and in a quantitative fashion.
Qualitatively, the presence of tumor enhancement in the pectoralis major muscle was temporally related to enhancement of the adjacent breast tumor. When tumor was present, the enhancement pattern was either infiltrative (without change in the muscle contour) or focal and masslike (with change in the muscle contour). These patterns correlated with the configuration and extent of tumor involvement of the muscle. When the pattern was infiltrative and mass effect was not present, the presence of contrast material to outline the extent of tumor spread was particularly helpful.
Because of the inability to place radiographic markers under MR guidance in the posterior aspect of the breast, this study lacks direct histologic and MR correlation with respect to the exact tumor margins. In musculoskeletal radiology, contrast-enhanced MR imaging may fail to allow differentiation of tumor from perineoplastic edema, which thus results in overestimation of the extent of disease (16). Further studies with improved radiographic and histologic correlation may help determine if overestimation occurs in tumor involving the pectoralis major muscle due to invasion from adjacent breast tumors.
Other modalities, such as computed tomography (CT), have been useful in assessing the presence of chest wall invasion by tumor (17,18). Reliable signs include mass effect or frank destruction of the underlying rib. Pectoralis major muscle involvement on CT images may be more difficult to detect and, unless mass effect is present, may not be suspected. MR imaging is superior to CT with respect to in-plane resolution, anatomic detail, and the ability to detect subtle enhancement within the muscles, which suggests its superiority in this setting.
Among our patients, MR imaging was able to contribute important local staging information for those with posterior breast tumors. Involvement of musculature deep to the tumor was reliably indicated by abnormal enhancement in the muscle. Obliteration of the fat plane between tumor and muscle alone did not indicate muscle involvement. This information was more reliably obtained with MR imaging than with mammography or physical examination. Therefore, the routine use of breast MR imaging should be considered for preoperative surgical planning in women with posterior breast tumors.
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Acknowledgments
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We thank Richard Fischer, RMRIT, and Charles Gregory Nyman, RMRIT, for assistance with patient imaging.
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Footnotes
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Author contributions: Guarantor of integrity of entire study, E.A.M.; study concepts and design, E.A.M., L.L.; definition of intellectual content, E.A.M., L.H.S., L.K.T., L.L., A.F.A., K.J.V.Z., D.D.D.; literature research, E.A.M., M.B.D.; clinical studies, E.A.M., L.H.S., L.K.T., L.L., A.F.A., D.D.D.; data acquisition and analysis, E.A.M., L.H.S., S.J.K., L.K.T.; statistical analysis, E.A.M., L.H.S., S.J.K.; manuscript preparation, editing, and review, E.A.M., L.H.S., M.B.D., L.L., A.F.A., K.J.V.Z., D.D.D.
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TOP
Abstract
Introduction
