Clinical Radiology 70 (2015) 523e527
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Incidental extra-mammary findings in breast MRI A.M. Alduk*, M. Prutki, R. Stern-Padovan Department of Radiology, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
art icl e i nformat ion Article history: Received 21 September 2014 Received in revised form 14 December 2014 Accepted 6 January 2015
AIM: To investigate the frequency, distribution, and nature of incidental extra-mammary findings detected with breast MRI. MATERIALS AND METHODS: Incidental findings were defined as unexpected lesions outside the breast, not previously known or suspected at the time of referral. Five hundred consecutive breast MRI studies performed from June 2010 to September 2012 were reviewed in this retrospective study for which the institutional review board granted approval and waived the requirement for informed consent. MRI findings were compared with subsequent diagnostic procedures in order to differentiate benign from malignant lesions. RESULTS: One hundred and thirty-eight incidental findings were found in 107 of the 500 (21.4%) examined patients. The most common site was the liver (61/138; 44.2%), followed by the lung (24/138; 17.4%), mediastinum (22/138; 15.9%), pleural cavity (15/138; 10.9%), bone tissue (9/138; 6.5%), spleen (3/138; 2.2%), major pectoral muscle (3/138; 2.2%), and kidney (1/138; 0.7%). Twenty-five of the 138 (18.1%) incidental findings were confirmed to be malignant, whereas the remaining 113 (81.9%) were benign. Malignant findings were exclusively detected in patients with known breast carcinoma, whereas incidental findings in patients without a history of carcinoma were all benign. Twenty-five of 100 (24.8%) incidental findings among patients with history of breast cancer were malignant. CONCLUSION: Although many of incidental findings were benign, some were malignant, altering the diagnostic work-up, staging, and treatment. Therefore, it is important to assess the entire field of view carefully for abnormalities when reviewing breast MRI studies. Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Breast cancer is the most frequent cancer among women in both developed and developing countries and the second leading cause of cancer death among women.1 Breast MRI is recognized as the most sensitive imaging technique for the detection, diagnosis, and staging of breast carcinoma. It is an imaging technique that is increasingly being
* Guarantor and correspondent: A.M. Alduk, Clinical Department for Diagnostic and Interventional Radiology, University Hospital Centre Zagreb, Kispaticeva 12, HR-10000 Zagreb, Croatia. Tel.: þ385 1 23 88 455; fax: þ385 1 23 88 250. E-mail address: [email protected] (A.M. Alduk).
used in clinical practice2 according to indications outlined by the European Society of Breast Cancer Specialists (EUSOMA).3 In addition to evaluating the breast and axillae, the field of view (FOV) of breast MRI includes part of the thorax and upper abdomen. Breast MRI examinations can therefore detect findings that are incidental to the initial indication. The detection and characterization of these extra-mammary findings represents a challenge to the interpreting physician, both in terms of assigning clinical significance and determining the appropriate work-up for a given abnormality. The purpose of the present study was to determine the frequency, distribution, and nature of incidental extra-mammary findings detected at breast MRI.
http://dx.doi.org/10.1016/j.crad.2015.01.003 0009-9260/Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
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A.M. Alduk et al. / Clinical Radiology 70 (2015) 523e527
Materials and methods Study population This retrospective study was granted approval by the institutional review board and the requirement for informed consent was waived. The electronic radiology information system was reviewed and 500 consecutive patients who underwent breast MRI studies from June 2010 to September 2012 were identified. All patients who underwent breast MRI during that period of time were included, regardless of indication.
MRI protocol Five hundred reviewed breast MRI examinations were performed using a 1.5 T MRI unit (Avanto, Siemens, Erlangen, Germany). The following sequences were evaluated: turbo inversion recovery magnitude (TIRM) axial sequence [repetition time (TR) ¼ 5600 ms, echo time (TE) ¼ 59 ms, bandwidth ¼ 252, matrix 1 0.7 1, section thickness ¼ 4 mm, interval ¼ 0.8 mm, field of view (FOV) ¼ 340 mm, number of excitations (NEX) ¼ 2], 3D T1-weighted non-fat saturated axial sequence (TR ¼ 8.6 ms, TE ¼ 4.7 ms, flip angle (FA) ¼ 20 , NEX ¼ 1, section thickness ¼ 1 mm, interval 20%, matrix 1 0.7 1, FOV ¼ 320 mm), 3D T1-weighted fat-saturated axial sequence (TR ¼ 4.06 ms, TE ¼ 1.65 ms, FA ¼ 10 , matrix ¼ 1 0.8 1.5, section thickness ¼ 1.5 mm, interval 20%, FOV ¼ 340 mm, NEX ¼ 1) before and five times after intravenous administration of 0.1 mmol/kg body weight of gadopentetate dimeglumine (Magnevist, Bayer Schering Pharma, Berlin, Germany). Contrast material was injected with a 15 s delay into the antecubital vein with a 20 G needle at a flow rate of 3.5 ml/s followed by a flush of 15 ml saline solution.
Interpretation All 500 breast MRI studies were reviewed independently by two radiologists with 4 and 7 years of experience in breast and body MRI, respectively. Extra-mammary incidental findings were reported and analysed. Through a systematic review of medical charts, the MRI findings were compared with subsequent diagnostic procedures. Abdominal ultrasound, skeletal scintigraphy, CT, combined positron-emission tomographyecomputed tomography (PET-CT), abdominal MRI, oesophagography, cytological, and histopathological analyses were analysed to confirm the presence and the nature of incidental findings suspected at MRI. The reference range for pleural effusions at breast MRI based on a healthy population is up to 7 mm on the right side and 5 mm on the left side.4 Pleural effusions smaller than this reference range were excluded from this study. According to current guidelines, the size criterion for detecting lymph node abnormalities was accepted and no biopsy of mediastinal lymph nodes was carried out. Mediastinal lymph nodes with short axis >10 mm were
considered abnormal, except for internal mammary lymph nodes where a size criterion of 5 mm was accepted.5 Incidental findings were categorized in terms of intrathoracic and extra-thoracic distribution, organ involved as well as malignant and non-malignant. The distribution of malignant findings in the two groups of patients depending on indication for the MRI study (with or without a history of cancer) was assessed.
Statistical analysis Categorical (nominal) variables were binary coded and frequencies presented as n (%), whilst numerical and ordinal variables were presented with median and range values. All statistics analyses were done using Excel Add-In Data Analysis (Microsoft Office Professional Plus 2010, Version: 14.0.6023.1000, Redmond, WA, USA).
Results Five hundred female patients (median age 59 years; range 29e85 years) were included in the study. The indications for MRI were follow-up assessment of patients with known breast cancer (n ¼ 210, 42%), preoperative assessment of patients with breast carcinoma (n ¼ 87, 17.4%), characterization of equivocal findings at conventional imaging (n ¼ 178, 35.6%), and screening of high-risk women (n ¼ 25, 5%). One hundred and thirty-eight incidental findings were found in 107 of the 500 (21.4%) patients examined. 73 of the 107 (68.2%) patients had a history of breast cancer and 34 (31.8%) had no history of breast cancer. Seventy-seven of the 138 (55.8%) incidental findings were intra-thoracic and 61 (44.2%) were extra-thoracic. The most common site was the liver (61/138; 44.2%), followed by the lung (24/138; 17.4%), mediastinum (22/138; 15.9%), pleural cavity (15/138; 10.9%), bone tissue (9/138; 6.5%), spleen (3/138; 2.2%), major pectoral muscle (3/138; 2.2%) and kidney (1/138; 0.7%). Twenty-five of the 138 (18.1%) incidental findings were confirmed to be malignant, whereas the remaining 113 (81.9%) were benign. Malignant findings were exclusively detected in patients with known breast carcinoma, whereas incidental findings in patients without a history of carcinoma were all benign. Twenty-five of 100 (25%) incidental findings among patients with a history of breast cancer were malignant. Unexpected malignant lesions were detected in three (3.4%) patients on preoperative breast MRI. Malignant findings included bone metastases (7/25; Fig 1), liver metastases (5/25), mediastinal lymph nodes (5/25), lung metastases (3/25), major pectoral muscle metastases (3/25), and pleural lesions (2/25; Fig 2). Benign findings included hepatic cysts (46/113; Fig 3), haemangiomas (9/113; Fig 4), dilated bile ducts (1/113), pulmonary scars (14/113; Fig 5), benign pulmonary nodules (6/113), pulmonary arteriovenous malformation (1/113), hiatal hernias (13/113), pericardial cyst (1/113), mediastinal lymphangioma (1/113), thymoma (1/113), dilated oesophagus (1/113), pleural effusion (14/113), bone trauma (2/113), splenomegaly (3/113), and renal cyst (1/113).
A.M. Alduk et al. / Clinical Radiology 70 (2015) 523e527
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Figure 1 Images in a 64-year-old woman with a history of breast cancer and an incidental sternal metastatic lesion. (a) Sagittal and (b) axial T1weighted unenhanced MRI images show a hypointense sternal lesion (arrow), which enhances on axial T1-weighted contrast-enhanced images (c). (d) CT image confirms the presence of bone metastasis.
Figure 2 Images in a 63-year-old woman with a history of breast cancer and pleural carcinosis. Axial T1-weighted MRI images before (a) and after the administration of contrast material (b) show bilateral pleural thickening with irregularity of the pleural contour (arrow).
Figure 3 A 54-year-old woman without a history of cancer. Axial T2-weighted MR images show hyperintense left liver lobe lesion (a) that is hypointense on axial T1-weighted images after the administration of contrast material (b). (c) CT image confirms the presence of a hepatic cyst.
Figure 4 Images in a 42-year-old woman without a history of breast cancer showing a hepatic haemangioma. (a) Axial TIRM image shows a large hyperintense liver lesion. (b) CT image after the administration of contrast material shows progressive enhancement of the lesion, which is the same density as the blood pool, that is characteristic of haemangioma.
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Figure 5 Images in a 61-year-old woman with a history of breast cancer and incidental finding of right middle lobe syndrome. (a) Axial TIRM image shows an area of linear hyperintense opacities. (b) CT image of the thorax demonstrates marked right middle lobe bronchiectasis with extensive volume loss, which is characteristic of right middle lobe syndrome.
Seven out of nine (77.9%) bone lesions turned out to be malignant, as well as 5/22 (22.7%) lesions located in mediastinum, 2/15 (13.3%) in pleural cavity, 3/24 (12.5%) in lungs, and 5/61 (8.2%) in liver. In the group of patients with a history of breast cancer, malignant lesions occurred more frequently: in 7/7 (100%) bone lesions, 5/16 (31.2%) mediastinal, 2/7 (28.2%) pleural cavity, 3/22(13.6%) lung, and 5/ 43(11.6%) liver lesions. No patients had a second primary carcinoma to account for malignant findings.
Discussion Few studies are published concerning the prevalence and nature of incidental extra-mammary findings at breast MRI. Morakkabati-Spitz et al.6 analysed the prevalence and type of incidental findings in 1013 patients undergoing breast MRI. Incidental findings were encountered in 9% of the patients, with a higher frequency in patients with a history of breast cancer. The prevalence of incidental malignant findings was 81% in patients examined for preoperative staging. Incidental benign and malignant findings were equally frequent in patients followed after breast cancer therapy. The incidental findings were exclusively benign in patients without a history of breast cancer. Rinaldi et al.7 reviewed 1535 breast MRI studies retrospectively and reported the prevalence of extra-mammary findings of 17.6% located most frequently in the liver (51.9%). Twenty point four percent of the incidental findings were malignant, and the positive predictive value for MRI to detect malignant lesion was high if located within the bone, lymph nodes, and lung, while it was low if located within the liver. Iodice et al.8 reviewed 828 MRI studies retrospectively and reported collateral findings in 34% of patients. Although the liver was the most common location (48%), only five liver lesions were malignant. The present study confirms that breast MRI may reveal a large number of incidental extra-mammary findings. It is consistent with previous studies in terms of frequency, distribution, and nature of incidental extra-mammary findings. Although most of the extra-mammary findings were benign, some were metastatic, typically requiring the use of systemic therapy.9e11 Malignant lesions were exclusively detected in patients with previously known breast
carcinoma, which emphasizes the importance of careful assessment of incidental findings in this group. The present study showed that the prevalence of malignant findings in patients with a history of breast cancer is dependent on location, with the high likelihood of bone lesions being malignant (100%) in comparison to other locations. This is probably due to the wide spectrum of benign abnormalities encountered in the liver (cysts and haemangiomas) or pleural cavity (effusions). Therefore, a new bone lesion in a patient with breast carcinoma should be considered malignant until proved otherwise and should prompt further diagnostic work-up. The majority of incidental liver lesions in patients with a history of breast carcinoma were benign (88.4%), representing mostly cysts and haemangiomas, which do not require further evaluation if unambiguous MRI features are present.12e15 However, 11.6% of hepatic lesions were metastatic, altering further treatment. This is why indeterminate lesions that do not satisfy the criteria for cysts or haemangiomas require further diagnostic work-up (using ultrasound, CT, or liver MRI). Among patients with preoperative breast MRI, none had lung metastases, although they can be found in 5e10% of breast cancer patients at presentation,16 altering the treatment plan. The reason is probably due to a limited role of breast MRI in the evaluation of lung nodules because of its limited spatial resolution compared with multidetector CT, high susceptibility differences between airspaces and the pulmonary parenchyma, and the presence of respiratory and cardiac motion. Most of small pulmonary nodules are benign, but metastases, bronchogenic carcinoma, and other malignant causes must be excluded. Pulmonary nodules
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Incidental extra-mammary findings in breast MRI A.M. Alduk*, M. Prutki, R. Stern-Padovan Department of Radiology, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
art icl e i nformat ion Article history: Received 21 September 2014 Received in revised form 14 December 2014 Accepted 6 January 2015
AIM: To investigate the frequency, distribution, and nature of incidental extra-mammary findings detected with breast MRI. MATERIALS AND METHODS: Incidental findings were defined as unexpected lesions outside the breast, not previously known or suspected at the time of referral. Five hundred consecutive breast MRI studies performed from June 2010 to September 2012 were reviewed in this retrospective study for which the institutional review board granted approval and waived the requirement for informed consent. MRI findings were compared with subsequent diagnostic procedures in order to differentiate benign from malignant lesions. RESULTS: One hundred and thirty-eight incidental findings were found in 107 of the 500 (21.4%) examined patients. The most common site was the liver (61/138; 44.2%), followed by the lung (24/138; 17.4%), mediastinum (22/138; 15.9%), pleural cavity (15/138; 10.9%), bone tissue (9/138; 6.5%), spleen (3/138; 2.2%), major pectoral muscle (3/138; 2.2%), and kidney (1/138; 0.7%). Twenty-five of the 138 (18.1%) incidental findings were confirmed to be malignant, whereas the remaining 113 (81.9%) were benign. Malignant findings were exclusively detected in patients with known breast carcinoma, whereas incidental findings in patients without a history of carcinoma were all benign. Twenty-five of 100 (24.8%) incidental findings among patients with history of breast cancer were malignant. CONCLUSION: Although many of incidental findings were benign, some were malignant, altering the diagnostic work-up, staging, and treatment. Therefore, it is important to assess the entire field of view carefully for abnormalities when reviewing breast MRI studies. Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Breast cancer is the most frequent cancer among women in both developed and developing countries and the second leading cause of cancer death among women.1 Breast MRI is recognized as the most sensitive imaging technique for the detection, diagnosis, and staging of breast carcinoma. It is an imaging technique that is increasingly being
* Guarantor and correspondent: A.M. Alduk, Clinical Department for Diagnostic and Interventional Radiology, University Hospital Centre Zagreb, Kispaticeva 12, HR-10000 Zagreb, Croatia. Tel.: þ385 1 23 88 455; fax: þ385 1 23 88 250. E-mail address: [email protected] (A.M. Alduk).
used in clinical practice2 according to indications outlined by the European Society of Breast Cancer Specialists (EUSOMA).3 In addition to evaluating the breast and axillae, the field of view (FOV) of breast MRI includes part of the thorax and upper abdomen. Breast MRI examinations can therefore detect findings that are incidental to the initial indication. The detection and characterization of these extra-mammary findings represents a challenge to the interpreting physician, both in terms of assigning clinical significance and determining the appropriate work-up for a given abnormality. The purpose of the present study was to determine the frequency, distribution, and nature of incidental extra-mammary findings detected at breast MRI.
http://dx.doi.org/10.1016/j.crad.2015.01.003 0009-9260/Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
524
A.M. Alduk et al. / Clinical Radiology 70 (2015) 523e527
Materials and methods Study population This retrospective study was granted approval by the institutional review board and the requirement for informed consent was waived. The electronic radiology information system was reviewed and 500 consecutive patients who underwent breast MRI studies from June 2010 to September 2012 were identified. All patients who underwent breast MRI during that period of time were included, regardless of indication.
MRI protocol Five hundred reviewed breast MRI examinations were performed using a 1.5 T MRI unit (Avanto, Siemens, Erlangen, Germany). The following sequences were evaluated: turbo inversion recovery magnitude (TIRM) axial sequence [repetition time (TR) ¼ 5600 ms, echo time (TE) ¼ 59 ms, bandwidth ¼ 252, matrix 1 0.7 1, section thickness ¼ 4 mm, interval ¼ 0.8 mm, field of view (FOV) ¼ 340 mm, number of excitations (NEX) ¼ 2], 3D T1-weighted non-fat saturated axial sequence (TR ¼ 8.6 ms, TE ¼ 4.7 ms, flip angle (FA) ¼ 20 , NEX ¼ 1, section thickness ¼ 1 mm, interval 20%, matrix 1 0.7 1, FOV ¼ 320 mm), 3D T1-weighted fat-saturated axial sequence (TR ¼ 4.06 ms, TE ¼ 1.65 ms, FA ¼ 10 , matrix ¼ 1 0.8 1.5, section thickness ¼ 1.5 mm, interval 20%, FOV ¼ 340 mm, NEX ¼ 1) before and five times after intravenous administration of 0.1 mmol/kg body weight of gadopentetate dimeglumine (Magnevist, Bayer Schering Pharma, Berlin, Germany). Contrast material was injected with a 15 s delay into the antecubital vein with a 20 G needle at a flow rate of 3.5 ml/s followed by a flush of 15 ml saline solution.
Interpretation All 500 breast MRI studies were reviewed independently by two radiologists with 4 and 7 years of experience in breast and body MRI, respectively. Extra-mammary incidental findings were reported and analysed. Through a systematic review of medical charts, the MRI findings were compared with subsequent diagnostic procedures. Abdominal ultrasound, skeletal scintigraphy, CT, combined positron-emission tomographyecomputed tomography (PET-CT), abdominal MRI, oesophagography, cytological, and histopathological analyses were analysed to confirm the presence and the nature of incidental findings suspected at MRI. The reference range for pleural effusions at breast MRI based on a healthy population is up to 7 mm on the right side and 5 mm on the left side.4 Pleural effusions smaller than this reference range were excluded from this study. According to current guidelines, the size criterion for detecting lymph node abnormalities was accepted and no biopsy of mediastinal lymph nodes was carried out. Mediastinal lymph nodes with short axis >10 mm were
considered abnormal, except for internal mammary lymph nodes where a size criterion of 5 mm was accepted.5 Incidental findings were categorized in terms of intrathoracic and extra-thoracic distribution, organ involved as well as malignant and non-malignant. The distribution of malignant findings in the two groups of patients depending on indication for the MRI study (with or without a history of cancer) was assessed.
Statistical analysis Categorical (nominal) variables were binary coded and frequencies presented as n (%), whilst numerical and ordinal variables were presented with median and range values. All statistics analyses were done using Excel Add-In Data Analysis (Microsoft Office Professional Plus 2010, Version: 14.0.6023.1000, Redmond, WA, USA).
Results Five hundred female patients (median age 59 years; range 29e85 years) were included in the study. The indications for MRI were follow-up assessment of patients with known breast cancer (n ¼ 210, 42%), preoperative assessment of patients with breast carcinoma (n ¼ 87, 17.4%), characterization of equivocal findings at conventional imaging (n ¼ 178, 35.6%), and screening of high-risk women (n ¼ 25, 5%). One hundred and thirty-eight incidental findings were found in 107 of the 500 (21.4%) patients examined. 73 of the 107 (68.2%) patients had a history of breast cancer and 34 (31.8%) had no history of breast cancer. Seventy-seven of the 138 (55.8%) incidental findings were intra-thoracic and 61 (44.2%) were extra-thoracic. The most common site was the liver (61/138; 44.2%), followed by the lung (24/138; 17.4%), mediastinum (22/138; 15.9%), pleural cavity (15/138; 10.9%), bone tissue (9/138; 6.5%), spleen (3/138; 2.2%), major pectoral muscle (3/138; 2.2%) and kidney (1/138; 0.7%). Twenty-five of the 138 (18.1%) incidental findings were confirmed to be malignant, whereas the remaining 113 (81.9%) were benign. Malignant findings were exclusively detected in patients with known breast carcinoma, whereas incidental findings in patients without a history of carcinoma were all benign. Twenty-five of 100 (25%) incidental findings among patients with a history of breast cancer were malignant. Unexpected malignant lesions were detected in three (3.4%) patients on preoperative breast MRI. Malignant findings included bone metastases (7/25; Fig 1), liver metastases (5/25), mediastinal lymph nodes (5/25), lung metastases (3/25), major pectoral muscle metastases (3/25), and pleural lesions (2/25; Fig 2). Benign findings included hepatic cysts (46/113; Fig 3), haemangiomas (9/113; Fig 4), dilated bile ducts (1/113), pulmonary scars (14/113; Fig 5), benign pulmonary nodules (6/113), pulmonary arteriovenous malformation (1/113), hiatal hernias (13/113), pericardial cyst (1/113), mediastinal lymphangioma (1/113), thymoma (1/113), dilated oesophagus (1/113), pleural effusion (14/113), bone trauma (2/113), splenomegaly (3/113), and renal cyst (1/113).
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Figure 1 Images in a 64-year-old woman with a history of breast cancer and an incidental sternal metastatic lesion. (a) Sagittal and (b) axial T1weighted unenhanced MRI images show a hypointense sternal lesion (arrow), which enhances on axial T1-weighted contrast-enhanced images (c). (d) CT image confirms the presence of bone metastasis.
Figure 2 Images in a 63-year-old woman with a history of breast cancer and pleural carcinosis. Axial T1-weighted MRI images before (a) and after the administration of contrast material (b) show bilateral pleural thickening with irregularity of the pleural contour (arrow).
Figure 3 A 54-year-old woman without a history of cancer. Axial T2-weighted MR images show hyperintense left liver lobe lesion (a) that is hypointense on axial T1-weighted images after the administration of contrast material (b). (c) CT image confirms the presence of a hepatic cyst.
Figure 4 Images in a 42-year-old woman without a history of breast cancer showing a hepatic haemangioma. (a) Axial TIRM image shows a large hyperintense liver lesion. (b) CT image after the administration of contrast material shows progressive enhancement of the lesion, which is the same density as the blood pool, that is characteristic of haemangioma.
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A.M. Alduk et al. / Clinical Radiology 70 (2015) 523e527
Figure 5 Images in a 61-year-old woman with a history of breast cancer and incidental finding of right middle lobe syndrome. (a) Axial TIRM image shows an area of linear hyperintense opacities. (b) CT image of the thorax demonstrates marked right middle lobe bronchiectasis with extensive volume loss, which is characteristic of right middle lobe syndrome.
Seven out of nine (77.9%) bone lesions turned out to be malignant, as well as 5/22 (22.7%) lesions located in mediastinum, 2/15 (13.3%) in pleural cavity, 3/24 (12.5%) in lungs, and 5/61 (8.2%) in liver. In the group of patients with a history of breast cancer, malignant lesions occurred more frequently: in 7/7 (100%) bone lesions, 5/16 (31.2%) mediastinal, 2/7 (28.2%) pleural cavity, 3/22(13.6%) lung, and 5/ 43(11.6%) liver lesions. No patients had a second primary carcinoma to account for malignant findings.
Discussion Few studies are published concerning the prevalence and nature of incidental extra-mammary findings at breast MRI. Morakkabati-Spitz et al.6 analysed the prevalence and type of incidental findings in 1013 patients undergoing breast MRI. Incidental findings were encountered in 9% of the patients, with a higher frequency in patients with a history of breast cancer. The prevalence of incidental malignant findings was 81% in patients examined for preoperative staging. Incidental benign and malignant findings were equally frequent in patients followed after breast cancer therapy. The incidental findings were exclusively benign in patients without a history of breast cancer. Rinaldi et al.7 reviewed 1535 breast MRI studies retrospectively and reported the prevalence of extra-mammary findings of 17.6% located most frequently in the liver (51.9%). Twenty point four percent of the incidental findings were malignant, and the positive predictive value for MRI to detect malignant lesion was high if located within the bone, lymph nodes, and lung, while it was low if located within the liver. Iodice et al.8 reviewed 828 MRI studies retrospectively and reported collateral findings in 34% of patients. Although the liver was the most common location (48%), only five liver lesions were malignant. The present study confirms that breast MRI may reveal a large number of incidental extra-mammary findings. It is consistent with previous studies in terms of frequency, distribution, and nature of incidental extra-mammary findings. Although most of the extra-mammary findings were benign, some were metastatic, typically requiring the use of systemic therapy.9e11 Malignant lesions were exclusively detected in patients with previously known breast
carcinoma, which emphasizes the importance of careful assessment of incidental findings in this group. The present study showed that the prevalence of malignant findings in patients with a history of breast cancer is dependent on location, with the high likelihood of bone lesions being malignant (100%) in comparison to other locations. This is probably due to the wide spectrum of benign abnormalities encountered in the liver (cysts and haemangiomas) or pleural cavity (effusions). Therefore, a new bone lesion in a patient with breast carcinoma should be considered malignant until proved otherwise and should prompt further diagnostic work-up. The majority of incidental liver lesions in patients with a history of breast carcinoma were benign (88.4%), representing mostly cysts and haemangiomas, which do not require further evaluation if unambiguous MRI features are present.12e15 However, 11.6% of hepatic lesions were metastatic, altering further treatment. This is why indeterminate lesions that do not satisfy the criteria for cysts or haemangiomas require further diagnostic work-up (using ultrasound, CT, or liver MRI). Among patients with preoperative breast MRI, none had lung metastases, although they can be found in 5e10% of breast cancer patients at presentation,16 altering the treatment plan. The reason is probably due to a limited role of breast MRI in the evaluation of lung nodules because of its limited spatial resolution compared with multidetector CT, high susceptibility differences between airspaces and the pulmonary parenchyma, and the presence of respiratory and cardiac motion. Most of small pulmonary nodules are benign, but metastases, bronchogenic carcinoma, and other malignant causes must be excluded. Pulmonary nodules
