Mammography

All About Mammography

The importance of high quality mammography has been established and mandated in the US

"A normal mammogram does not exclude cancer - Dr Sneh Bhargava Senior Radiologist Sitaram Bhartia Institute of Science & Research

Each modality and technique in mammography has its advantages and limitations. However, X-Ray Mammography has been accepted as the 'gold standard' against which all other techniques are compared. This paper deals with X- Ray Mammography only. The modalities are as follows:

• Conventional X-Ray mammography.
• Digital breast mammography and tomosynthesis.
• Sono-mammography. lMRI mammography.

The first two modalities use ionisng radiations while last two use non- ionising radiations of Ultrasound and magnetic resonance.

X-Ray Mammography

It is recommended to be carried out for two specific reasons which is either for diagnostic or for screening purposes.

Diagnostic Mammography

Diagnostic Mammography is indicated when there is a clinically palpable breast lump, nipple discharge, nipple retraction, axillary lump or pain in the breast. The purpose of the exam is to analyse the nature of the lump and the discharge, whether it is benign or malignant. Both breasts are examined for purposes of comparison and to exclude synchronous breast cancer and to serve as a base line screen for follow up.

The golden rule to follow in case of breast lumps is the triad of clinical examination, X-ray mammography and fine needle aspiration cytology. then only has justice been done to a breast lump.

Screening Mammography

It is indicated in all healthy women over 40 years with no breast complaints because cancer breast is the number one cancer killer in women in the world and in the cities of Mumbai and Delhi in India. It can be detected before it is clinically palpable. There is plenty of evidence to prove that early detection can lead to cure and bring down mortality and morbidity. Most developed countries like the US, the UK, Canada and Scandinavia have annual national screening programmes. Although it is a common malignancy in those countries much more than in India, the vast majority of women will not have breast cancer in a given year. The mammography effort is designed to find the few women (one to five per 1,000) who do have breast cancer each year which is not palpable. We in India do not have a national screening programme because of limited financial resources available for healthcare and many other priorities that plague the majority of the population. However, with increasing awareness, voluntary screening is taking place as preventive programmes. Therefore, the necessity of training manpower to evaluate those individuals who volunteer for screening and those patients who have breast lumps, specific training is a must.

Technology, Techniques and Training

As a rule, both breasts must be evaluated. We know 20 per cent mammograms in cancer breast will be normal, even if a mass is clinically palpable, therefore a normal mammogram does not exclude cancer. The potential of mammography is to detect cancer early.

Two views of each breast, craniocaudal and mediolateral are done on a dedicated mammography unit and they usually suffice for diagnostic purposes. However, facilities for magnification of suspicious areas, optimum compression based on individual breast characteristics, most suitable anode / filter combinations for least radiation dose and optimal image quality are available in the most technically advanced units. Facilities of stereotactic needle localisation in non-palpable suspicious lesions are also available for precise excisional surgery, early diagnosis and treatment. Thus, technology for early diagnosis and action is available today. Training is what we must focus on.

Standards of Mammography

the importance of high quality mammography has been established and mandated in the US by the Mammography Quality Standards Act (MQSA) of 1994. We have no such standard mandated in our country. Recognising the need to provide clear and accurate reports, the American College of Radiology had developed BI-RADS- Breast Image Reporting and Data System. BI-RADS is a quality assurance tool and guide to standardising breast imaging reports for improved communication and facilitate outcome monitoring and reduce ambiguity of reports between referring physicians, researchers and patients. It allows radiologists to relate the degree of concern for malignancy through a concise description using approved terminology and to give clear management recommendations. This format has now been extended to include Ultra-Sound (US) and Magnetic Resonance Imaging (MRI) of the breast. The rationale behind the development is to reduce confusion and increase clarity of breast imaging reports and to develop a common language so that data can be pooled and image interpretation refined with a decision oriented final assessment that provides guidance for future care.

The breast imaging lexicon includes description of the following

Masses

Space occupying lesions, seen in two projections, their location, their size, shape, outline and margin characteristics. A common problem of reporting has been clarified. A margin is sharply demarcated when at least 75 per cent of it is well defined with the remainder no worse than obscured by overlapping normal appearing tissue.

Asymmetry

Global asymmetry is recognised by BI-RADS as a normal variation and is only of concern if it corresponds to a palpable abnormality. Focal asymmetry requires a 6 month interval follow up for two years to be sure that it remains stable.

Calcifications

• Typically benign.
• Intermediate concern - suspicious and
• High probability of malignancy.

Benign

They are skin deposits and vascular calcifications which are easily distinguishable. Others are coarse popcorn calcifications like in involuting fibroadenomas and rod like ones of secretary deposits, punctate ones that are very small (under 0.5 mm) lucent centered deposits of fat necrosis, egg shell and rim calcifications in borders of masses. The inter mediate suspicious ones should have a biopsy when present in an irregular cluster. Higher probability of malignancy is present in pleomorphic, heterogeneous, sand like calcifications conforming to a ductal network or fine linear branching calcifications.

BIRADS also requires the to include a statement of general breast tissue type with four categories originally described by Wolfe: -

Category one: Breast is entirely fat (less than 25 per cent fibroglandular).

Category two: 25 -50 per cent is fibroglandular and scattered.

Category three: 51-75 per cent is fibroglandular and heterogeneously dense which could obscure detection of small masses.

Category four: More than 75 per cent is fibro-glandular and extremely dense which lowers the sensitivity of the mammogram.

These should be subjected to additional Ultrasound or MRI mammography if clinically suspicious. Associated findings of skin thickening, nipple retraction or nipple areolar abnormality and axillary nodes should be included in the evaluation and documented. Final BIRADS assessment categories according to the American College of Radiology are as follows:

Important Considerations

Images obtained on X-Ray Mammogram are age and hormone related. Thus, a balance between information retrieval and radiation dose received has to be made in every case. Below age 30 years the breast tissue is dense on an X-Ray mammogram and information retrieval is low and so is the incidence of cancer, but incidence of benign disease is high, therefore it is prudent to perform sonomammography rather than a conventional X-ray mammography as the first study. It also saves the child bearing age of the women from radiation exposure which is vital and important. Above age 30 years even if a breast mass feels benign clinically, X-ray mammogram should be done for further evaluation of the mass and to search for and exclude micro-calcification by using magnification techniques either by a hand lens or by magnification technique on the machine itself. In other words every effort should be made to exclude malignancy by follow up and FNAC if necessary.

If these considerations are adhered to and a properly calibrated dedicated X-Ray Unit used with proper compression, digital processing of the films and getting optimal image quality with low radiation dose, you have done your job. Lastly, BIRADS systems of reporting should be adopted, then only you would have delivered world class healthcare. Therefore, quality standards must be mandated and legalised.

Conclusion

The ACR-BI-RADS final assessment categories have validated the efficacy of the descriptors and assessment categories and has helped to effectively communicate findings, degree of concern for malignancy and recommendations to both clinicians and patients. There is no other system available currently that accomplishes what BI-RADS has done. Continued auditing, research, refinement and revisions are to be expected and we should adopt and propagate its use for continued improvement and better patient care in our country.

drsneh.bhargava@gmail.com