REVIEW ARTICLE
Breast Magnetic Resonance Imaging Incidental Findings Janet Szabo, MD (Top Magn Reson Imaging 2014;23: 361–371)
B
reast magnetic resonance imaging (MRI) is now an integral part of breast imaging. It makes valuable contributions in high-risk screening; evaluating the extent of disease, positive surgical margins, and response to neoadjuvant chemotherapy; as well as distinguishing postoperative scar from recurrent disease.1–6 Although the examination is focused on the breast, portions of the neck, thorax, and upper abdomen are also visualized. Just as in computed tomography, the issue of the incidental or unexpected finding must be addressed by the reader. The detection of these findings during diagnosis and surveillance often results in additional testing, economic burden, and anxiety for the patient. Most incidentally detected lesions are benign; however, the reader must consider the potential of these findings to be metastases or additional primary tumors. Approximately 5% to 10% of breast cancers are metastatic at the time of diagnosis.7 Even with significant advances in breast cancer treatment, up to 70% of node-positive breast cancers will relapse and 20% to 30% of women with stage I and II disease will develop distant metastases, occurring approximately 15 years after radiation therapy.7,8 Therefore, all detected findings must be carefully considered. A recent study demonstrated the bone, lung, and liver to be the most common anatomical sites of distant metastases in patients with breast cancer, with 21.9% presenting with multisite involvement.9 The exception to this pattern is the basal-like and triple-negative breast cancers, which have a predilection for visceral and central nervous system metastases and infrequently involve bone.10 Although lesion detection occurs on potentially any sequence, the 3-dimensional fast spoiled gradient echo axial sequence is reported to be superior to the short tau inversion recovery sequence in incidental finding detection (82.8% vs 76.5%).11 As in computed tomography, the addition of intravenous contrast enhances lesion detection. Rinaldi et al11 demonstrated the enhanced 3-dimensional fast spoiled gradient echo axial fat-suppressed axial sequence to have greater sensitivity compared with unenhanced images in detecting metastatic lesions, especially those smaller than 10 mm (98.3% vs 79.3%). These lesions are often on the edge of the field of view and require window manipulation for identification.
BREAST During the initial extent of disease evaluation, it is not uncommon to discover additional breast lesions. Management of ipsilateral breast findings is directed by their morphology, enhancement characteristics, and proximity to the index tumor. Masses found in the contralateral breast during the extent of disease evaluation raise the issue of an additional primary tumor.
From the Ichan School of Medicine at Mount Sinai, New York, NY. Reprints: Janet Szabo, MD, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (e‐mail: [email protected]). The author declares no conflict of interest. Copyright ©2014 by Lippincott Williams & Wilkins
Studies have reported an incidence of contralateral synchronous malignancy detected by preoperative MRI to be in the range of 3% to 5 %.12–14 A contralateral metachronous cancer has been reported to develop in 5% to 10% of patients with breast cancer within a 10-year follow-up.12 This is especially important in BRCA1/2 mutation carriers, who have a significantly higher risk of developing a contralateral breast cancer (53%) in contrast to the general population (2%).15
EXTRAMAMMARY Additional extramammary findings also are common, and most are benign. Recent retrospective studies of breast MRI examinations report 17% to 34% of cases with at least 1 extramammary incidental finding.11,16,17 In one large study, approximately 20% of incidental findings were determined to be malignant.11 Only 14% to 20% of benign findings were reported to be clinically relevant.16,17 Normal variants such as situs inversus (Fig. 1) require no additional evaluation. Common benign findings such as hiatal hernia (Fig. 2) and postoperative change (Figs. 3 and 4) are well-recognized, posing no burden to the reader. It is the identification of other potentially significant findings that creates the dilemma. A personal history of malignancy and the anatomical location influence the risk associated with these extramammary findings. A recent study identified a 36% prevalence of malignant incidental findings in the group of patients with personal breast cancer compared with 8% in those with no known breast cancer.16 The positive predictive value (PPV) of MRI to identify a metastasis is high for incidental lesions detected in the bone (PPV, 89%), lymph nodes (PPV, 83%), and lung parenchyma (PPV, 59%) but low with those lesions discovered in the liver (PPV, 9%) or associated with pleural effusion (PPV, 6%).11
BONE The patient's medical history is highly important in evaluating incidental bone lesions. Although many lesions may be benign, the skeleton is the most common anatomical site of distant metastases in patients with breast cancer.9 Hemangioma is a common, benign vascular lesion usually identified in the lower thoracic and upper lumbar vertebrae (Fig. 5). It is reported in approximately 10% to 12% of all autopsy cases.18 Usually asymptomatic, they may be multiple in up to 30% of the cases, particularly in the thoracic spine. Degenerative change in the spine is a common finding detected on MRI sequences. Classic patterns of altered signal intensity and multiple flowing osteophytes are well recognized on the sagittal sequences. A large solitary osteophyte seen on the axial sequence may raise the possibility of a pulmonary or posterior mediastinal mass (Fig. 6). Osseous metastases are present in most women who die of metastatic breast cancer and reported to be the first exclusive site of metastatic disease in 41.1% of cases.9,19 Kennecke et al20 reported that the bone is the most likely metastatic site for all breast cancer subtypes, with the exception of basal-type tumors, which have high rates of lung metastases. These bony metastases often occur late in the course of early-stage breast cancer as demonstrated by Berman et al.9 This correlates with a recent UK
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FIGURE 3. Magnetic susceptibility artifact from sternal wire sutures. FIGURE 1. Situs inversus.
study, which demonstrated a less than 1% incidence of osseous metastases in patients with stage 1 breast cancer during the first 5 years of follow-up.21 Asymmetric or altered marrow signal may be an early sign of bony metastasis (Fig. 7).
LYMPH NODES Evaluation of lymph nodes status is an extremely important part of the initial extent of disease evaluation and surveillance examinations. Because benign lymph nodes can show enhancement with a prominent washout kinetic pattern, detection of abnormal lymph nodes has relied heavily on morphology as in both computed tomography (CT) and ultrasound evaluation. Nodes that display irregular margins, cortical thickening, a round rather than reniform shape, and a short-axis dimension of 10 mm or larger are suspicious. Changes in ipsilateral axillary, internal mammary chain, and supraclavicular nodes should raise the possibility of regional recurrence. Internal mammary chain nodal disease is uncommon without coexistent axillary involvement (Fig. 8).
It is important to remember that patients with a history of silicone implants may have nodal enlargement related to extruded silicone. In a postmastectomy patient with silicone reconstruction regional nodal enlargement may be caused by silicone lyphadenitis and metastases (Fig. 9).
LUNG Pulmonary parenchymal findings, especially masses and airspace disease, are significant. Two recent studies reported high rates of malignancy in the incidentally detected pulmonary lesions ranging from 55% to 83%, including both metastases and primary lung cancer11,16 (Fig. 10). The lung is reported to be the second most common anatomical site for distant metastases in patients with breast cancer (22.4%).9 Computed tomography is needed to accurately characterize these lesions. Comparison with previous cross-sectional imaging is a valuable tool for assessing the potential significance of these findings, often helping to establish stability in cases of granuloma, linear atelectasis, and scarring (Figs. 11 and 12).
LIVER The liver is the most common site of reported incidental findings, and the majority is benign. This includes both solid and cystic masses. The probability of a hepatic lesion being malignant is less than 20% even in patients with a known malignancy.22,23 The incidence of simple hepatic cysts is reported to be up to 17% in CT series, 20% in surgery series, and 52% of the general population in postmortem examinations24–28(Fig. 13). Hepatic hemangioma is the most common benign tumor of the liver, with a reported incidence ranging up to 20%25,29(Fig. 14). The liver, however, is also a common site of extranodal metastatic disease, found in up to 36% of all patients.30 It is reported to be the third most common anatomical site for distant metastases occurring in patients with stage I and II breast cancer treated with breast conservation therapy (7.3%).9 The presence of multiple masses with indistinct or irregular margins and heterogeneous signal intensity influence the decision to recommend additional evaluation (Fig. 15).
Spleen FIGURE 2. Hiatal hernia.
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Incidental splenic findings are uncommon and are rarely significant (Fig. 16). A recent study of more than 3000 cases reported that the prevalence of splenic granuloma was 1.38% and ©2014 Lippincott Williams & Wilkins
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Breast MRI Incidental Findings
FIGURE 4. Upper abdominal artifact associated with gastric lap band identified on MRI and CT.
FIGURE 5. Thoracic vertebral hemangioma detected as a focal area of altered signal intensity on the right side of the vertebral body on breast MRI (A) with subsequent dedicated thoracic spine MRI evaluation (B).
FIGURE 6. Thoracic osteophyte simulating a right-sided posterior mediastinal mass (arrow) on breast MRI. Corresponding heavily calcified posterior osteophyte identified on chest CT. ©2014 Lippincott Williams & Wilkins
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FIGURE 7. Bony metastases presenting as altered signal intensity. A, Right scapular metastasis from occult pulmonary carcinoma detected on screening breast MRI as asymmetric signal intensity in the marrow. Positron emission tomography (PET)/CT demonstrating corresponding abnormal fluorodeoxyglucose accumulation in the left lung primary carcinoma and right scapular metastasis. B and C, Metastatic breast carcinoma involving the head of the left clavicle (curved arrow) and right scapula (straight arrow) with corresponding coronal PET/CT images documenting abnormal fluorodeoxyglucose accumulation.
FIGURE 8. Left axillary and internal mammary adenopathy (arrow) associated with ipsilateral breast cancer.
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FIGURE 9. Enlarged internal mammary (arrows) and axillary lymph nodes in a postmastectomy patient with a ruptured implant and silicon lymphadenitis seen on unenhanced T1 sagittal, enhanced T1 fat-saturated sagittal, unenhanced T2-weighted axial, and enhanced sagittal sequences.
FIGURE 10. Occult left lung cancer presenting as a faintly visible pulmonary mass on breast MRI with subsequent diagnostic chest CT.
FIGURE 11. Left lung nodule identified on enhanced T1-weighted fat saturation breast MRI sequence found to be stable compared with multiple previous unenhanced chest CT examinations. ©2014 Lippincott Williams & Wilkins
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FIGURE 12. Right middle lobe scarring stable over a 2-year period.
FIGURE 13. Benign hepatic cyst on enhanced T1-weighted MRI and enhanced CT images.
that of accessory spleen was 0.1%; splenic cyst and hemangioma were each detected in less than 0.08%.31
age group.32,33 The management of renal masses and complex cysts is well documented in the CT literature34(Fig. 18).
KIDNEY
THYROID
Simple renal cysts are common incidental findings (Fig. 17). They are generally asymptomatic and require no intervention. The reported prevalence, which increases with age, ranges from 5% to 41%, reflecting the selected diagnostic imaging modality and
Thyroid nodules are very common, with only a minority being malignant (Fig. 19). Recent studies demonstrated incidental thyroid findings in 16% to 18% of patients on cross-sectional imaging, but less than 10% were malignant.35,36
FIGURE 14. Hepatic hemangioma identified in the localizing sequence as a T1 hyperintense mass with no corresponding mass identified on the enhanced T1-weighted fat-saturated axial sequence. Liver ultrasound performed 8 years earlier demonstrates a hyperechoic mass consistent with hemangioma in this area of the right lobe.
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FIGURE 15. Hepatic metastases associated with breast cancer involving both the right (A) and the left (B) lobes of the liver seen on breast MRI localizing sequence with confirmatory PET/CT coronal images.
FIGURE 16. Benign hepatic and splenic cysts seen on unenhanced T1 and enhanced T1 fat-saturated axial images. ©2014 Lippincott Williams & Wilkins
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FIGURE 17. Incidental renal cyst identified on the localizing sagittal sequence and renal ultrasound.
FIGURE 18. A, Right renal mass not displaying signal intensity compatible with a cyst seen on localizing MRI sequence. B, Abdomen CT confirming the presence of a complex partially calcified mass in the right kidney.
Gallbladder
Chest Wall
Cholelithiasis is frequently encountered and well recognized as filling defects of varying size within a fluid-filled gallbladder (Fig. 20). It affects approximately 10% to 20% of the adult population in developed countries, and the majority are asymptomatic, with only 2% to 4% of patients becoming symptomatic annually.37,38 Gallbladder cancer is uncommon, with approximately 5000 cases per year in the United States.39
Chest wall masses, which arise from bone or soft tissue, may be asymptomatic, with approximately 20% being found incidentally on imaging.42 Both benign and malignant masses may present as asymmetric breast enlargement (Fig. 22). The appearance of tumor
Pleural Fluid The normal amount of physiologic pleural fluid is reported to be between 4 and 18 mL.40 A recent study of screening breast MRI patients demonstrated that small visible amounts of pleural fluid were not only common (87%) but also frequently bilateral (62%).41 In that study, pleural fluid measuring less than or equal to 7 mL on the right and 5 mL on the left was considered within normal range.41 Thus, the presence of detectable pleural fluid should not be a cause for a clinical evaluation (Fig. 21). However, in patients with a personal history of breast cancer, the presence of pleural effusion associated with pleural nodules and focal or circumferential thickening is suspicious.
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FIGURE 19. Enlarged thyroid. ©2014 Lippincott Williams & Wilkins
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Breast MRI Incidental Findings
FIGURE 20. Cholelithiasis identified in axial, sagittal, and coronal planes.
FIGURE 21. Physiological pleural fluid seen on T2-weighted short tau inversion recovery sequences. ©2014 Lippincott Williams & Wilkins
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FIGURE 22. Asymmetric breast enlargement due to chest wall hemangioma seen on enhanced T1-weighted fat saturation axial and sagittal MRI sequences (A and B), enhanced chest CT (C), and preablation arteriogram (D).
on the ipsilateral chest wall after mastectomy or breast conservation therapy is referred to as a local recurrence. Approximately 5% to 10% of patients undergoing mastectomy are reported to have chest wall recurrence, which may be isolated or present with concomitant regional disease within 10 years of surgery.43 This often presents as tumor nodules in the skin or subcutaneous tissue and may involve the mastectomy scar. Invasion of the chest wall musculature is less frequent.43
CONCLUSIONS Interpretation of breast MRI during both the initial diagnostic extent of disease evaluation and follow-up surveillance should include a careful search of adjacent anatomy to identify any additional lesions, which could impact the treatment plan and prognosis. Incidental findings on breast MRI are common and usually benign, with hepatic cysts being the most frequent. A small number of patients have significant findings that merit additional diagnostic evaluation. Patients with personal history of breast cancer, regardless of stage, need careful assessment of all incidental findings, especially those involving the skeleton and lung. Patients that carry the BRCA 1/2 germ line mutations have an increased risk of developing a contralateral breast cancer.
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REFERENCES 1. Kuhl CK. MR imaging for surveillance of women at high familial risk for breast cancer. Magn Reson Imaging Clin N Am. 2006;14:391–402. 2. Chae EY, Cha JH, Kim HH, et al. Evaluation of residual disease using breast MRI after excisional biopsy for breast cancer. AJR Am J Roentgenol. 2013;200:1167–1173. 3. Kim JA, Son EJ, Kim EK, et al. Postexcisional breast magnetic resonance imaging in patients with breast cancer: predictable findings of residual cancer. J Comput Assist Tomogr. 2009;33:940–994. 4. Kriege M, Brekelmans CT, Boetes C, et al. Magnetic resonance imaging screening study group. Efficacy of MRI and mammography for breast-cancer screening in women with a familial or genetic predisposition. N Engl J Med. 2004;351:427–437. 5. Lee CH, Dershaw DD, Kopans D, et al. Breast cancer screening with imaging: recommendations from the Society of Breast Imaging and the ACR on the use of mammography, breast MRI, breast ultrasound, and other technologies for the detection of clinically occult breast cancer. J Am Coll Radiol. 2010;7:18–27. 6. Hylton NM, Blume JD, Bernreuter W, et al. Locally advanced breast cancer: MR imaging for prediction of response to neoadjuvant chemotherapy—results from ACRIN 6657/I-SPY TRIAL 1. Radiology. 2012;263:663–672.
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7. Cardoso F, Harbeck N, Fallowfield L, et al. Locally recurrent or metastatic breast cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2012;23(suppl 7):vii11–vii19.
24. Ros PR, Erturk SM. Benign tumors of the liver. In: Gore RM, Levine MS, eds. Textbook of Gastrointestinal Radiology. Philadelphia, PA: Saunders; 2008:1591–1622.
8. Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Effects of chemotherapy and hormonal therapy for early breast cancer on recurrence and 15-year survival: an overview of the randomised trials. Lancet. 2005;365:1687–1717.
25. Snover DC. Non-neoplastic liver disease. In: Mills EC, Carter D, Greeson JK, eds. Sternberg's Diagnostic Surgical Pathology. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:1167–1191.
9. Berman AT, Thukral AD, Hwang W, et al. Incidence and patterns of distant metastases for patients with early-stage breast cancer after breast conservation treatment. Clin Breast Cancer. 2013;13:88–94. 10. Dent R, Hanna W, Trudeau M, et al. Pattern of metastatic spread in triple-negative breast cancer. Breast Cancer Res Treat. 2009;115:423–428. 11. Rinaldi P, Constantini M, Belli P, et al. Extra-mammary findings in breast MRI. Eur Radiol. 2011;21:2268–2276. 12. Taneja S, Jena A, Zaidi S, et al. MRI evaluation of the contralateral breast in patients with recently diagnosed breast cancer. Indian J Radiol Imaging. 2012;22:69–73. 13. Liberman L, Morris EA, Kim CM, et al. MR imaging findings in the contralateral breast in women with recently diagnosed breast cancer. AJR Am J Roentgenol. 2003;180:333–341. 14. Lehman CD, Gatsonis C, Kuhl CK, et al; ACRIN Trial 6667 Investigators Group. MR evaluation of the contralateral breast in women with recently diagnosed breast cancer. N Engl Med. 2007;356:1295–1303. 15. Rogozińska-Szczepka J, Utracka-Hutka B, Grzybowska E, et al. BRCA1 and BRCA2 mutations as prognostic factors in bilateral breast cancer patients. Ann Oncol. 2004;15:1373–1376. 16. Moschetta M, Telegrafo M, Rella L, et al. Let’s go out of the breast: prevalence of extra-mammary findings and their characterization on breast MRI. Eur J Radiol. 2014;83:930–934. 17. Iodice D, Di Donato O, Liccardo I, et al. Prevalence of extramammary findings on breast MRI: a large retrospective single-centre study. Radiol Med. 2013;118:1109–1118. 18. Ross JS. Hemangioma. In: Spine. 1st ed. Salt Lake City, UT: Amirsys; 2004;IV1 14–16. 19. Solomayer EF, Diel IJ, Meyberg GC, et al. Metastatic breast cancer: clinical course, prognosis, and therapy related to the first site of metastases. Breast Cancer Res Treat. 2000;59:1–8. 20. Kennecke H, Yerushalmi R, Woods R, et al. Metastatic behavior of breast cancer subtypes. Clin Oncol. 2010;28:3271–3277. 21. Hagberg KW, Taylor A, Hermandez RH, et al. Incidence of bone metastases in breast cancer patients in the United Kingdom: results of a multi-database linkage study using the general practice research database. Cancer Epidemiol. 2013;37:240–246. 22. Khalil HI, Patterson SA, Panicek DM. Hepatic lesions deemed too small to characterize at CT: prevalence and importance in women with breast cancer. Radiology. 2005;235:872–878. 23. Schwartz LH, Gandras EJ, Colangelo SM, et al. Prevalence and importance of small hepatic lesions found at CT in patients with cancer. Radiology. 1999;210:71–74.
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26. Washington K, Harris E. Masses of the liver. In: Mills EC, Carter D, Greeson JK, eds. Sternberg's Diagnostic Surgical Pathology. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:1192–2023. 27. Carrim ZI, Murchison JT. The prevalence of simple renal and hepatic cysts detected by spiral computed tomography. Clin Radiol. 2003;58:626–629. 28. Oto A, Tamm EP, Zklaruk J. Multidetector row CT of the liver. Radiol Clin North Am. 2005;43:827–848. 29. Bioulac-Sage P, Laumonier H, Laurent C, et al. Benign and malignant vascular tumors of the liver in adults. Semin Liver Dis. 2008;28:302–314. 30. Washington K. Masses of the liver. In: Odze R, Goldblum JR, eds. Surgical Pathology of the GI Tract, Liver, Biliary Tract and Pancreas. 2nd ed. New York, NY: Elsevier; 2009:657–789. 31. Ekeh AP, Walusimbi M, Brigham E, et al. The prevalence of incidental findings on abdominal computed tomography scans of trauma patients. J Emerg Med. 2010;38:484–489. 32. Chang CC, Kuo JY, Chan WL, et al. Prevalence and clinical characteristics of simple renal cysts. J Chin Med Assoc. 2007;70:486–491. 33. Eknoyan G. A clinical view of simple and complex renal cysts. J Am Soc Nephrol. 2009;20:1874–1876. 34. Silverman SG, Israel GM, Herts BR, et al. Management of the incidental renal mass. Radiology. 2008;249:16–31. 35. Nguyen XV, Choudhury KR, Eastwood JD, et al. Incidental thyroid nodules on CT: evaluation of 2 risk-categorization methods for work-up of nodules. Am J Neuroradiol. 2013;34:1812–1817. 36. Yoon DY, Chang SK, Choi CS, et al. The prevalence and significance of incidental thyroid nodules identified on computed tomography. J Comput Assist Tomogr. 2008;32:810–815. 37. Gibney EJ. Asymptomatic gallstones. Br J Surg. 1990;77:368–372. 38. Frossard JL, Bonvin F. Charcot's triad. Int J Emerg Med. 2011;4:18. 39. Stinton LM, Shaffer EA. Epidemiology of gallbladder disease: cholelithiasis and cancer. Gut Liver. 2012;6:172–187. 40. Noppen M, De Waele M, Li R, et al. Volume and cellular content of normal pleural fluid in humans examined by pleural lavage. Am J Respir Crit Care Med. 2000;162:1023–1026. 41. Nguyen J, Nicholson B, Patrie J, et al. Incidental pleural effusions detected on screening breast mri. AJR Am J Roentgenol. 2012;199: W142–W145. 42. Shah AA, D'Amico TA. Primary chest wall tumors. J Am Coll Surg. 2010;210:360–366. 43. Freedman G, Fowble B. Local recurrence after mastectomy or breast-conserving surgery and radiation. Oncology. 2000;14:1561–1581.
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Breast Magnetic Resonance Imaging Incidental Findings Janet Szabo, MD (Top Magn Reson Imaging 2014;23: 361–371)
B
reast magnetic resonance imaging (MRI) is now an integral part of breast imaging. It makes valuable contributions in high-risk screening; evaluating the extent of disease, positive surgical margins, and response to neoadjuvant chemotherapy; as well as distinguishing postoperative scar from recurrent disease.1–6 Although the examination is focused on the breast, portions of the neck, thorax, and upper abdomen are also visualized. Just as in computed tomography, the issue of the incidental or unexpected finding must be addressed by the reader. The detection of these findings during diagnosis and surveillance often results in additional testing, economic burden, and anxiety for the patient. Most incidentally detected lesions are benign; however, the reader must consider the potential of these findings to be metastases or additional primary tumors. Approximately 5% to 10% of breast cancers are metastatic at the time of diagnosis.7 Even with significant advances in breast cancer treatment, up to 70% of node-positive breast cancers will relapse and 20% to 30% of women with stage I and II disease will develop distant metastases, occurring approximately 15 years after radiation therapy.7,8 Therefore, all detected findings must be carefully considered. A recent study demonstrated the bone, lung, and liver to be the most common anatomical sites of distant metastases in patients with breast cancer, with 21.9% presenting with multisite involvement.9 The exception to this pattern is the basal-like and triple-negative breast cancers, which have a predilection for visceral and central nervous system metastases and infrequently involve bone.10 Although lesion detection occurs on potentially any sequence, the 3-dimensional fast spoiled gradient echo axial sequence is reported to be superior to the short tau inversion recovery sequence in incidental finding detection (82.8% vs 76.5%).11 As in computed tomography, the addition of intravenous contrast enhances lesion detection. Rinaldi et al11 demonstrated the enhanced 3-dimensional fast spoiled gradient echo axial fat-suppressed axial sequence to have greater sensitivity compared with unenhanced images in detecting metastatic lesions, especially those smaller than 10 mm (98.3% vs 79.3%). These lesions are often on the edge of the field of view and require window manipulation for identification.
BREAST During the initial extent of disease evaluation, it is not uncommon to discover additional breast lesions. Management of ipsilateral breast findings is directed by their morphology, enhancement characteristics, and proximity to the index tumor. Masses found in the contralateral breast during the extent of disease evaluation raise the issue of an additional primary tumor.
From the Ichan School of Medicine at Mount Sinai, New York, NY. Reprints: Janet Szabo, MD, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (e‐mail: [email protected]). The author declares no conflict of interest. Copyright ©2014 by Lippincott Williams & Wilkins
Studies have reported an incidence of contralateral synchronous malignancy detected by preoperative MRI to be in the range of 3% to 5 %.12–14 A contralateral metachronous cancer has been reported to develop in 5% to 10% of patients with breast cancer within a 10-year follow-up.12 This is especially important in BRCA1/2 mutation carriers, who have a significantly higher risk of developing a contralateral breast cancer (53%) in contrast to the general population (2%).15
EXTRAMAMMARY Additional extramammary findings also are common, and most are benign. Recent retrospective studies of breast MRI examinations report 17% to 34% of cases with at least 1 extramammary incidental finding.11,16,17 In one large study, approximately 20% of incidental findings were determined to be malignant.11 Only 14% to 20% of benign findings were reported to be clinically relevant.16,17 Normal variants such as situs inversus (Fig. 1) require no additional evaluation. Common benign findings such as hiatal hernia (Fig. 2) and postoperative change (Figs. 3 and 4) are well-recognized, posing no burden to the reader. It is the identification of other potentially significant findings that creates the dilemma. A personal history of malignancy and the anatomical location influence the risk associated with these extramammary findings. A recent study identified a 36% prevalence of malignant incidental findings in the group of patients with personal breast cancer compared with 8% in those with no known breast cancer.16 The positive predictive value (PPV) of MRI to identify a metastasis is high for incidental lesions detected in the bone (PPV, 89%), lymph nodes (PPV, 83%), and lung parenchyma (PPV, 59%) but low with those lesions discovered in the liver (PPV, 9%) or associated with pleural effusion (PPV, 6%).11
BONE The patient's medical history is highly important in evaluating incidental bone lesions. Although many lesions may be benign, the skeleton is the most common anatomical site of distant metastases in patients with breast cancer.9 Hemangioma is a common, benign vascular lesion usually identified in the lower thoracic and upper lumbar vertebrae (Fig. 5). It is reported in approximately 10% to 12% of all autopsy cases.18 Usually asymptomatic, they may be multiple in up to 30% of the cases, particularly in the thoracic spine. Degenerative change in the spine is a common finding detected on MRI sequences. Classic patterns of altered signal intensity and multiple flowing osteophytes are well recognized on the sagittal sequences. A large solitary osteophyte seen on the axial sequence may raise the possibility of a pulmonary or posterior mediastinal mass (Fig. 6). Osseous metastases are present in most women who die of metastatic breast cancer and reported to be the first exclusive site of metastatic disease in 41.1% of cases.9,19 Kennecke et al20 reported that the bone is the most likely metastatic site for all breast cancer subtypes, with the exception of basal-type tumors, which have high rates of lung metastases. These bony metastases often occur late in the course of early-stage breast cancer as demonstrated by Berman et al.9 This correlates with a recent UK
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FIGURE 3. Magnetic susceptibility artifact from sternal wire sutures. FIGURE 1. Situs inversus.
study, which demonstrated a less than 1% incidence of osseous metastases in patients with stage 1 breast cancer during the first 5 years of follow-up.21 Asymmetric or altered marrow signal may be an early sign of bony metastasis (Fig. 7).
LYMPH NODES Evaluation of lymph nodes status is an extremely important part of the initial extent of disease evaluation and surveillance examinations. Because benign lymph nodes can show enhancement with a prominent washout kinetic pattern, detection of abnormal lymph nodes has relied heavily on morphology as in both computed tomography (CT) and ultrasound evaluation. Nodes that display irregular margins, cortical thickening, a round rather than reniform shape, and a short-axis dimension of 10 mm or larger are suspicious. Changes in ipsilateral axillary, internal mammary chain, and supraclavicular nodes should raise the possibility of regional recurrence. Internal mammary chain nodal disease is uncommon without coexistent axillary involvement (Fig. 8).
It is important to remember that patients with a history of silicone implants may have nodal enlargement related to extruded silicone. In a postmastectomy patient with silicone reconstruction regional nodal enlargement may be caused by silicone lyphadenitis and metastases (Fig. 9).
LUNG Pulmonary parenchymal findings, especially masses and airspace disease, are significant. Two recent studies reported high rates of malignancy in the incidentally detected pulmonary lesions ranging from 55% to 83%, including both metastases and primary lung cancer11,16 (Fig. 10). The lung is reported to be the second most common anatomical site for distant metastases in patients with breast cancer (22.4%).9 Computed tomography is needed to accurately characterize these lesions. Comparison with previous cross-sectional imaging is a valuable tool for assessing the potential significance of these findings, often helping to establish stability in cases of granuloma, linear atelectasis, and scarring (Figs. 11 and 12).
LIVER The liver is the most common site of reported incidental findings, and the majority is benign. This includes both solid and cystic masses. The probability of a hepatic lesion being malignant is less than 20% even in patients with a known malignancy.22,23 The incidence of simple hepatic cysts is reported to be up to 17% in CT series, 20% in surgery series, and 52% of the general population in postmortem examinations24–28(Fig. 13). Hepatic hemangioma is the most common benign tumor of the liver, with a reported incidence ranging up to 20%25,29(Fig. 14). The liver, however, is also a common site of extranodal metastatic disease, found in up to 36% of all patients.30 It is reported to be the third most common anatomical site for distant metastases occurring in patients with stage I and II breast cancer treated with breast conservation therapy (7.3%).9 The presence of multiple masses with indistinct or irregular margins and heterogeneous signal intensity influence the decision to recommend additional evaluation (Fig. 15).
Spleen FIGURE 2. Hiatal hernia.
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Incidental splenic findings are uncommon and are rarely significant (Fig. 16). A recent study of more than 3000 cases reported that the prevalence of splenic granuloma was 1.38% and ©2014 Lippincott Williams & Wilkins
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FIGURE 4. Upper abdominal artifact associated with gastric lap band identified on MRI and CT.
FIGURE 5. Thoracic vertebral hemangioma detected as a focal area of altered signal intensity on the right side of the vertebral body on breast MRI (A) with subsequent dedicated thoracic spine MRI evaluation (B).
FIGURE 6. Thoracic osteophyte simulating a right-sided posterior mediastinal mass (arrow) on breast MRI. Corresponding heavily calcified posterior osteophyte identified on chest CT. ©2014 Lippincott Williams & Wilkins
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FIGURE 7. Bony metastases presenting as altered signal intensity. A, Right scapular metastasis from occult pulmonary carcinoma detected on screening breast MRI as asymmetric signal intensity in the marrow. Positron emission tomography (PET)/CT demonstrating corresponding abnormal fluorodeoxyglucose accumulation in the left lung primary carcinoma and right scapular metastasis. B and C, Metastatic breast carcinoma involving the head of the left clavicle (curved arrow) and right scapula (straight arrow) with corresponding coronal PET/CT images documenting abnormal fluorodeoxyglucose accumulation.
FIGURE 8. Left axillary and internal mammary adenopathy (arrow) associated with ipsilateral breast cancer.
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FIGURE 9. Enlarged internal mammary (arrows) and axillary lymph nodes in a postmastectomy patient with a ruptured implant and silicon lymphadenitis seen on unenhanced T1 sagittal, enhanced T1 fat-saturated sagittal, unenhanced T2-weighted axial, and enhanced sagittal sequences.
FIGURE 10. Occult left lung cancer presenting as a faintly visible pulmonary mass on breast MRI with subsequent diagnostic chest CT.
FIGURE 11. Left lung nodule identified on enhanced T1-weighted fat saturation breast MRI sequence found to be stable compared with multiple previous unenhanced chest CT examinations. ©2014 Lippincott Williams & Wilkins
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FIGURE 12. Right middle lobe scarring stable over a 2-year period.
FIGURE 13. Benign hepatic cyst on enhanced T1-weighted MRI and enhanced CT images.
that of accessory spleen was 0.1%; splenic cyst and hemangioma were each detected in less than 0.08%.31
age group.32,33 The management of renal masses and complex cysts is well documented in the CT literature34(Fig. 18).
KIDNEY
THYROID
Simple renal cysts are common incidental findings (Fig. 17). They are generally asymptomatic and require no intervention. The reported prevalence, which increases with age, ranges from 5% to 41%, reflecting the selected diagnostic imaging modality and
Thyroid nodules are very common, with only a minority being malignant (Fig. 19). Recent studies demonstrated incidental thyroid findings in 16% to 18% of patients on cross-sectional imaging, but less than 10% were malignant.35,36
FIGURE 14. Hepatic hemangioma identified in the localizing sequence as a T1 hyperintense mass with no corresponding mass identified on the enhanced T1-weighted fat-saturated axial sequence. Liver ultrasound performed 8 years earlier demonstrates a hyperechoic mass consistent with hemangioma in this area of the right lobe.
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FIGURE 15. Hepatic metastases associated with breast cancer involving both the right (A) and the left (B) lobes of the liver seen on breast MRI localizing sequence with confirmatory PET/CT coronal images.
FIGURE 16. Benign hepatic and splenic cysts seen on unenhanced T1 and enhanced T1 fat-saturated axial images. ©2014 Lippincott Williams & Wilkins
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FIGURE 17. Incidental renal cyst identified on the localizing sagittal sequence and renal ultrasound.
FIGURE 18. A, Right renal mass not displaying signal intensity compatible with a cyst seen on localizing MRI sequence. B, Abdomen CT confirming the presence of a complex partially calcified mass in the right kidney.
Gallbladder
Chest Wall
Cholelithiasis is frequently encountered and well recognized as filling defects of varying size within a fluid-filled gallbladder (Fig. 20). It affects approximately 10% to 20% of the adult population in developed countries, and the majority are asymptomatic, with only 2% to 4% of patients becoming symptomatic annually.37,38 Gallbladder cancer is uncommon, with approximately 5000 cases per year in the United States.39
Chest wall masses, which arise from bone or soft tissue, may be asymptomatic, with approximately 20% being found incidentally on imaging.42 Both benign and malignant masses may present as asymmetric breast enlargement (Fig. 22). The appearance of tumor
Pleural Fluid The normal amount of physiologic pleural fluid is reported to be between 4 and 18 mL.40 A recent study of screening breast MRI patients demonstrated that small visible amounts of pleural fluid were not only common (87%) but also frequently bilateral (62%).41 In that study, pleural fluid measuring less than or equal to 7 mL on the right and 5 mL on the left was considered within normal range.41 Thus, the presence of detectable pleural fluid should not be a cause for a clinical evaluation (Fig. 21). However, in patients with a personal history of breast cancer, the presence of pleural effusion associated with pleural nodules and focal or circumferential thickening is suspicious.
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FIGURE 19. Enlarged thyroid. ©2014 Lippincott Williams & Wilkins
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FIGURE 20. Cholelithiasis identified in axial, sagittal, and coronal planes.
FIGURE 21. Physiological pleural fluid seen on T2-weighted short tau inversion recovery sequences. ©2014 Lippincott Williams & Wilkins
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FIGURE 22. Asymmetric breast enlargement due to chest wall hemangioma seen on enhanced T1-weighted fat saturation axial and sagittal MRI sequences (A and B), enhanced chest CT (C), and preablation arteriogram (D).
on the ipsilateral chest wall after mastectomy or breast conservation therapy is referred to as a local recurrence. Approximately 5% to 10% of patients undergoing mastectomy are reported to have chest wall recurrence, which may be isolated or present with concomitant regional disease within 10 years of surgery.43 This often presents as tumor nodules in the skin or subcutaneous tissue and may involve the mastectomy scar. Invasion of the chest wall musculature is less frequent.43
CONCLUSIONS Interpretation of breast MRI during both the initial diagnostic extent of disease evaluation and follow-up surveillance should include a careful search of adjacent anatomy to identify any additional lesions, which could impact the treatment plan and prognosis. Incidental findings on breast MRI are common and usually benign, with hepatic cysts being the most frequent. A small number of patients have significant findings that merit additional diagnostic evaluation. Patients with personal history of breast cancer, regardless of stage, need careful assessment of all incidental findings, especially those involving the skeleton and lung. Patients that carry the BRCA 1/2 germ line mutations have an increased risk of developing a contralateral breast cancer.
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