Magnetic Resonance Imaging (MRI) and malignancy detection
The MRI scan is very sensitive for detecting invasive carcinoma, usually very close to 100% in fact. For Ductal Carcinoma In-Situ (DCIS) , the MRI scan sensitivity range is 40% to 100%. This holds true even when the breast lesion is not detectable using other imaging methods such as mammogram, X-ray or physical examination.
With MRI using an injected contrast agent, cancers become brighter and more easy to diagnose. This is an advantage that MRI has over both mammography and ultrasound.
This page is getting pretty old, but still very useful. However, I just want to let you know that I have created a newer page with more up-to-date information on MRI and Malignancy Detection.
Malignant-looking borders/outer margins of a lesion
The features of a malignant breast condition on MRI scan are often to do with the outer irregular borders of a lesion. Indeed, malignant lesions commonly feature irregular or spiculated borders or rim-enhancement on the periphery of the lesion.
On the other hand, features which suggest a more benign condition might be a mass with:-
- smooth and lobulated borders
- or with minimal or no enhancement
- a mass with non enhancing internal septations
- patchy parenchymal enhancement
MRI Scan and Contrast Enhancement
MRI scans of the breast almost always use an intravenous injection of a medicine that enhances the visibility of lesions. Sometimes radiologists refer to this process as a dynamic contrast enhanced MRI scan or DCE MRI.
The medicine is called an “MRI contrast agent”, and it works by making lesions appear brighter on the MRI scan images than the surrounding normal tissue.
This increase in contrast between normal and abnormal tissue makes the lesion easier for the radiologist to see, helping to distinguish between benign and malignant tumors.
Malignant and Benign Tumors on MRI Scan
During the MRI scan, a malignant lesion will tend to demonstrate a rapid increase in signal intensity (within the first 1 to 2 minutes) after the contrast injection. This intensity is often followed by a ‘wash-out’ (the lesion becomes less bright) of contrast on images which appear in the minutes that follow.
Benign lesions, on the other hand, tend to exhibit a slow, progressive rise in intensity of the signal with no wash-out of contrast. Radiologists classify the contrast enhanced lesion according to the morphology of the contrast, and also by the ‘kinetics‘ or changes in time of the contrast enhancing areas.
In addition, please note that MRI scan improves contrast and definition and not just cancer. MRI scan also improves definition in non-cancerous and pre-cancerous conditions, such as:-
- radial scar
- atypical hyperplasia
- lobular neoplasia
- sclerosing adenosis
- fat necrosis
Even though the MRI scan is very useful in determining whether or not a tumor is malignant, the ‘specificity’, which means the ability to correctly predict on the MRI report that a lesion is truly benign, is limited.
This is due to the overlap in the morphologic appearance on MRI scan with enhancement of both benign and malignant lesions.
However, MRI expertise in determining the ‘specificity’ of MRI scan data continues to rise. Indeed, the specificity of the MRI scan is over 80% for solid masses of 1 cm or larger.
MRI breast cancer screening may be beneficial for some higher risk groups
Sometimes MRI screening is useful for women who have a personal or familial history of breast cancer. MRI screening for women with a hereditary disposition of breast cancer has proven to be clinically valuable, finding about 12% more malignancies than traditional screening methods.
And, a high percentage of breast cancers that MRI scans find are at the DCIS or minimal breast cancer stage.
However, breast cancer MRI screening is not practical on a large scale. However, various focus groups conclude that the use of MRI in breast cancer screening may be useful for women who, for a variety of reasons, possess a 20% to 25% increased lifetime risk of breast cancer development.
There does seem to be agreement that women:-
- who have had prior treatments for Hodgkin disease
- with a family history of either ovarian or breast cancer,
be included in this higher-risk, MRI-recommended group.
However, there is insufficient convincing evidence and no consensus that other ‘high risk‘ women, for example, those with dense breast tissue and even women with atypical hyperplasia, require MRI screening.
Common Q&A’s on MRI Scan and Malignancy detection
When would a patient have an MRI scan ?
a patient would have an MRI scan after a biopsy that is positive for cancer, and your doctor needs more information about the extent of the disease.
In certain situations, such as for women with high risk of breast cancer, breast MRI may be useful with mammograms as a screening tool for detecting breast cancer.
Why is MRI done?
Breast MRI is most often used to screen for breast cancer in women thought to have a high risk of the disease. Your doctor may recommend a breast MRI scan if you have a diagnosis of breast cancer to determine the extent of the cancer.
MRI scans are also useful if you have a:-
- leak or rupture of a breast implant
- high risk of breast cancer
- strong family history of breast cancer
- very dense breast tissue and mammogram didn’t detect a prior breast cancer
- history of precancerous breast changes such as atypical hyperplasia or lobular carcinoma in situ
- strong family history of breast cancer and dense breast tissue
What does an MRI Scan show?
Like CT scans, MRI creates cross-section pictures of your insides. But MRI uses strong magnets, instead of radiation, to make the images.
An MRI scan can take cross sectional views from many angles, as if someone were looking at a slice (view) of your body from the front, from the side, or from above your head.
MRI creates pictures of soft tissue parts of the body that are sometimes hard to see using other imaging tests. MRI is very good at finding and pinpointing some cancers.
An MRI with contrast dye is the best way to see brain tumors. Using MRI, doctors can sometimes tell if a tumor is benign (not cancer) or malignant (cancer). MRI is also useful for looking for signs that cancer may have metastasized (spread) to another part of the body.
MRI images can also help doctors plan treatment such as surgery and/or radiation therapy.
How does an MRI scan work?
An MRI scanner is a cylinder or tube that holds a large, very strong magnet. As you lie on the table that slides within the tube, the device surrounds you with a powerful magnetic field.
The magnetic source then causes the centers of hydrogen atoms in your body to line up in one direction. Once the atoms are in line, the MRI machine then gives off a burst of radio frequency waves.
These waves cause the hydrogen nuclei to change direction. When they return to their original position, they give off certain signals that the scanner detects. Hydrogen nuclei in the body tissues change directions in different ways. A computer takes signals from these changes and converts them into a black and white picture.
What are some known risks for MRI?
A breast MRI is a safe procedure that does not expose you to radiation. But as with other tests, a breast MRI has risks such as a risk of false-positive results, or a risk of reaction to the contrast dye used.
How do I prepare for my MRI appointment?
Schedule your MRI for the beginning of your menstrual cycle. Also tell your doctor about any:-
- allergies you have
- kidney problems
- if you are, or think you may be, pregnant
- if you are still breast feeding
- implants such as pacemakers
Furthermore, do not wear anything metallic during the MRI scan.
Are there any possible complications?
Some people become very uneasy and even panic when lying inside the MRI scanner.
Other patients may also react to the contrast material. Symptoms of a reaction may include:-
- pain at the needle site
- a headache that develops a few hours after the test is over
- low blood pressure
- Fainting or feeling lightheaded (this is rare)
Be sure to let your health care team know if you have any of these symptoms.
What else should I know about MRI screening?
People who are overweight may have trouble fitting into the MRI machine.
The use of MRI scan during pregnancy has not been well studied, MRI is usually not done in the first 12 weeks of pregnancy unless there is a strong medical reason to use it.
Do not bring any credit cards or other items with magnetic scanning strips with you into the exam room (the magnet could wipe out the information stored on them).
MRI does not expose you to radiation but not all hospitals and imaging centers have dedicated breast MRI equipment available.
- Saslow D, Boetes C, Burke W, Harms S, Leach MO, Lehman CD, Morris E. (et al). (2007) American Cancer Society Breast Cancer Advisory Group.American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography. CA Cancer J Clin.(Mar. 2007) 57(2):75-89. https://www.ncbi.nlm.nih.gov/pubmed/17392385
- Orel SG, Schnall MD. (2001) MR imaging of the breast for the detection, diagnosis, and staging of the breast cancer. Radiology 2001; 220:13-30. https://www.ncbi.nlm.nih.gov/pubmed/11425968
More references for this post are on this page.