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Imaging Pathway of Breast Cancer

Author: Valerie Ulai - Medical Imaging Science

Breast cancer is the most common form of cancer in American women and second only to lung cancer as the most frequent cause of cancer death [1]. It is an uncontrolled growth of breast cells known as a Tumor [2]. A tumor can be benign or malignant; [2]


Benign tumors are not cancerous: Their cells are close to normal cell appearance, they grow slowly and they do not invade nearby tissues or spread to other parts of the body

Malignant tumors are cancerous: left unchecked, malignant cells can eventually spread beyond the original tumor to other parts of the body.

Hence, breast cancer is a malignant tumor that develops from the cells in the breast. Its common site of development is; [2]


Cells of lobules: the milk producing glands

Ducts: the passage that drains milk from the lobules to the nipple.


Less commonly, breast cancer can begin in the stromal tissues that includes the Fatty and Fibrous connective tissues of the breast [2].


Overtime, cancer can invade nearby healthy breast tissues and make its way into the underarm lymph nodes (small organs that filter out foreign substances in the body). When cancer gets into the lymph nodes, they then have a pathway into other parts of the body [2].

Thus, breast cancer is always caused by genetic abnormality that is either inherited from the parents or happen as a results of aging process. In contrast, some of its risk factors are smoking, drinking alcohol and unhealthy diet [2].

Furthermore, the stages of breast cancer are assessed by the American Joint committee on Cancer (AJCC) known as the TNM staging system [3].


Tumor (T): How large is the primary tumor in the breast? What are its biomarkers?

Node (N): Has the tumor spread to the lymph nodes? If so, where, what size, and how many?

Metastasis (M): Has the cancer spread to other parts of the body?


The results are combined to determine the stage of cancer for each person [3]. There are five (5) stages of breast cancer and is usually expressed as a number on a scale of 0 through IV- with stage 0 describing non-invasive cancers that remain within their original location and stage IV describing invasive cancers that have spread or metastases outside the breast to other parts of the body [4]. Staging can be clinical or pathological [3].

Clinical staging is based on the results of tests done before surgery which include the physical examinations and imaging modalities of mammogram, ultrasound (US) and Magnetic Resonance Imaging (MRI) scans [1, 4]. Pathological staging is based on what is found during surgery to remove breast tissue and lymph nodes [4].The results of pathological staging are usually available several days after surgery [3].

Imaging of breast cancer is done to assess breast for any abnormality. Breast screening is basically done on asymptomatic patients and diagnostic breast imaging is done on symptomatic patients. Symptoms of breast cancer are; lump in the breast, bloody discharge from the nipple and changes in the shape or texture of the nipple or breast [1, 3].

Mammography is the primary modality for breast imaging, except in young women where ultrasound (US) is often more appropriate [1]. MRI is used for staging breast cancer after Mammogram and US [1].

The imaging pathway of breast cancer is; [1, 4]

  1. Mammogram: Is a specific breast imaging modality that uses low dose radiation and compression devices to image breast with routine views of bilateral craniocaudal (CC) and mediolateral (MLO). It is inexpensive, widely available, non-invasive and it reduces mortality of breast cancer.

Mammographic findings of cancer are;

i. Malignant microcalcifications

ii. Visible mass, non-cystic on US

iii. Architectural distortion, especially with a central density

iv. Other less reliable secondary signs

In asymptomatic women mammography is used to find clinically occult breast cancer. In the symptomatic patient it is used to evaluate the area of clinical concern, as well as the remainder of the breasts. Hence, mammograms are the best breast screening and diagnostic modality.


2. Ultrasound (US): Uses sound waves and gel to produce real time images of the breasts using linear probes. It is an important adjunct to mammography and it is the primary imaging modality in less than 30 years of patients with breast problems. US is used to assess areas of mammographic or palpable abnormality. The US can differentiate a cyst from a solid mass, but cannot distinguish a benign solid from a malignant solid lesion with a high degree of accuracy. In dense breasts particularly, the US can detect cancers that may not be visible mammographically. The majority of palpable abnormalities are evaluated with both US and mammography: either to confirm and characterize the presence of abnormal breast tissue or to assess the changes which may be normal with mammography. In patients <30 years in whom breast cancer is rare, US has a primary role in the initial evaluation of a solitary breast mass to limit the radiation exposure in young women, using mammography. If the mass is a cyst, no further evaluation is required. If the mass is solid or not visible with the US, a single view mammogram primarily looking for microcalcifications can be performed, prior to possible biopsy.

Limitations of ultrasound are;

i. Limited visualizations of calcifications

ii. Most incidental findings benign

iii. Operator dependent

iv. Time consuming


3. Magnetic Resonance Imaging (MRI): Is an advanced imaging modality that uses magnetic waves to produce 2D and 3D images of the human body. MRI of breast cancer requires an IV contrast of gadolinium. At present MRI is still in the investigational stage of the breast and should be confined to certain difficult clinical cases. Decisions for clinical management must be made in conjunction with mammographic and clinical information.

The potential uses of MRI include;

i. treatment planning for breast conservation therapy,

ii. early detection of recurrent cancer,

iii. assessment of changes following surgery or chemotherapy and

iv. The evaluation of breast implants for rupture as well as the overlying native breast.

For metastasis breast cancer, MRI is more accurate than mammography and the US because it has a high sensitivity (98-100%). Breast MRI is not meant to replace mammography. Hence, MRI screening can detect otherwise occult cancer but it has not yet been shown to decrease mortality (life expectancy from breast cancer).

Limitation of MRI in breast cancer is low specificity (37-97%), lengthy examination and its expensive.


4. Interventional Techniques: After detecting the cyst or solid mass, tissue samples can be obtained with core biopsy almost as easily as Fine needle aspiration biopsy (FNAB). Employing stereotactic localization technique, a core biopsy needle can be placed in a lesion with pin-point accuracy, proving histological samples.


The treatment of breast cancer depends on the stage of cancer found after imaging [2]. It may consist of chemotherapy, radiation and surgery [1, 2].


There are some steps such as eating a balanced diet, maintaining a healthy weight, not smoking, limiting alcohol, and exercise regularly that women can take to limit the risk of getting breast cancer [2].


Breast cancer is a common cancer in women with more frequent deaths that is always almost caused by genetic abnormality. Hence, screening of breast is paramount for early detection and treatment. Mammography is the screening and diagnostic modality of choice for palpable breast for women above 30 years of age. Ultrasound is for women less than 30 years of age that present with breast cancer symptoms, because ultrasound is safe and does not use radiation. MRI and interventional techniques can also be used after the mammographic and ultrasound results that confirm cyst or solid mass. The treatment of breast after imaging consists of chemotherapy, radiation and surgery.


Reference:

  1. Pape. R. 2019. Female reproductive system. Powerpoint. Comparative Imaging-Course Code: 2.49906. University Of Papua New Guinea. August 2019.

  2. Breastcancer.org. what is breast Cancer? Retrieved from: https://www.breastcancer.org/symptoms/understand_bc/what_is_bc

  3. Cancer. Net. Breast Cancer: Stages. Retrieved from: https://www.cancer.net/cancer-types/breast-cancer/stages

  4. Summerton, S.L. Womens Imaging-SS-. Powerpoint. Retrieved from: https://www.learningradiology.com/powerpoint

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