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Indian Journal for the Practising Doctor

Breast Mammography: Pictorial Review

Author(s): Chhavi Kaushak

Vol. 4, No. 1 (2007-03 - 2007-04)

Chhavi Kaushak

Dr Chhavi Kaushak, MD, is from the Department of Radiology, Dr Ram Manohar Lohia Hospital, New Delhi 110001.
Correspondence: Dr Chhavi Kaushak, C/O Mr A P Kaushik, 516 NIMRI Colony, Ashok Vihar Phase IV, Delhi 110 052. [Email: drchhavi [email protected]]

In India, breast cancer is the second common malignancy after cervical cancer and is detected in 20 per 1,00,000 women. The incidence is increasing in most countries at the rate of 1-2% annually and soon nearly one million women will be developing this disease every year throughout the world. Imaging of the breast aims at early diagnosis of breast lesions, differentiation of benign from malignant lesions and detection of tiny cancers before they are symptomatic or palpable. It is possible to demonstrate the malignancy of the breast quite accurately by radiological examinations when the clinical examination has failed or when there is no clinical suspicion. Radiological evaluation also is of great help in differentiating breast lesions which clinically may mimic cancer and thereby helps in planning the correct line of treatment. Radiological Investigation may not replace biopsy but in fact it tends to invoke its use more judiciously.

Mammography is the basic imaging technique and so far the best screening modality for breast cancer. Film screen mammography has high resolution and contrast, detects spiculations and microcalcificaitons, and allows appreciation of subtle differences among soft tissue densities, and is known to have high sensitivity but low specificity for breast lesions. Two standard views, Cranio-caudal and Mediolateral-Oblique Views, of each breast are taken, with appropriate marker placed on the axillary side of the object table.

Supplementary views eg. spot compression and spot magnification views are taken whenever required. Appropriate exposure factors for breasts of different thickness are selected by the automatically set control panel of the machine. The quality of the mammograms should be assessed, and if not optimal, repeat examinations may be ordered. Mammograms of the right and left breasts are first placed back to back (mirror images) for comparable projections. Lighting should be homogenous, and adequate viewing conditions should be maintained. The mammograms are inspected carefully. The search is done systematically through similar areas in both breasts, comparing them all the times.

First, breast symmetry, size, general density, and glandular distribution are observed. Next, a search for masses, densities, calcifications, architectural distortions, and associated findings is performed. For masses, the shape, margins, and density are analyzed. Malignant lesions tend to have irregular and (usually) spiculated margins. Malignancies, especially scirrhous cancers, also tend to have density greater than that of the normal breast tissue. Very low density, such as that of fat, is seen in benign lesions (eg, oil cyst, lipomas, galactoceles, hamartomas).

Benign calcifications are usually larger than calcifications associated with malignancy. They are usually coarser, often round with smooth margins, and more easily seen. Benign calcifications tend to have specific shapes: eggshell calcifications in cyst walls, tramlike in arterial walls, popcorn type in fibroadenomas, large and rodlike with possible branching in ectatic ducts, and small calcifications with a lucent center in the skin.

Calcifications associated with malignancy are usually small (<0.5 mm) and often require the use of a magnifying glass to see them well. They tend to have a pleomorphic or heterogeneous shape or a fine granular, fine linear, or branching (casting) shape.

The distribution of calcification should be specified as grouped (clustered), linear, segmental, regional, or diffuse. Special findings, such a linear density that might represent a duct filled with secretions or reniform shape of intramammary lymph nodes (with a radiolucent center) may be encountered.

Associated findings are then taken into account. These include skin or nipple retraction, skin thickening (which may be focal or diffuse), trabecular thickening, skin lesions, axillary adenopathy, or architectural distortion.

The seen lesion is located by using the views either of the inner or outer or the lower or upper quadrants. It may also be central or retroareolar. The lesion can be described in a clockwise position. The breast is viewed as the face of a clock with the patient facing the observer. The depth of the lesion is assigned to anterior, middle, or posterior third of the breast. If previous examination results are available, their comparison is useful in assessing disease progress

This article provides a comprehensive review on specific mammographic features of various breast pathologies. The Breast Imaging Reporting and Data System (BIRADS) lexicon was developed by the American College of Radiology (ACR) to standardize mammographic reporting. The lesions were assigned a (BIRAD) Category as follows:

BIRAD 0 Needs further imaging
BIRAD 1 Negative study
BIRAD 2 Benign finding
BIRAD 3 Probably Benign finding
BIRAD 4 Suspicious abnormality
BIRAD 5 Highly suggestive of malignancy
BIRAD 6 Known Biopsy-Proven Malignancy


Category Care Plan and Comments
1 Continue annual screening mammography for women 40 years or older.
2 Continue annual screening mammography for women 40 years or older. This category is for
3 Usually, 6-month follow-up mammography is performed. Most category 3 abnormalities are not
4 Most category 4 abnormalities are benign but may require biopsy.
5 Classic signs of cancer are seen on the mammogram. All category 5 abnormalities are typically
6 Appropriate action should be taken

Mammographic lesions commonly associated with likely features are discussed below. It is important to know that these rules are not always followed by the lesions and there may be exceptional presentations in a small but significant segment of patients.

FIBROADENOMAS

Fibroadenoma is a smooth, rubbery or hard lump that moves easily within the breast tissue. It is most often found in teenagers and younger women. A fibroadenoma is typically not cancerous. Fibroadenomas are solid, smooth, firm, benign lumps that are most commonly found in women in their late teens and early 20s. They are the most common benign lumps that occur in women and can occur in women of any age. Increasingly, they are being seen in postmenopausal women who are taking hormone replacement therapy. The painless lump feels rubbery and moves around freely and very often is found by the woman herself. They vary in size and can grow anywhere in the breast tissue. Fibroadenomas are usually less than 5 cm in size and are located in UOQ of breast followed by UIQ. On mammography, they show well-defined or partially obscured margins because of the overlap of normal breast parenchyma. They are round to oval in shape and the density of fibroadenomas is equal to or less than the glandular breast tissue. Calcifications when present are usually coarse type. Some fibroadenomas may show presence of a partial or complete halo.

SIMPLE CYSTS

Cysts are fluid filled sacs within the breast. These sacs form when normal milk producing glands enlarge. The cause of this enlargement is not definitely known but is very likely related to an imbalance between the normal production and absorption of fluid. Breast cysts may be solitary but are most commonly multiple and can be of variable sizes. Breast cysts are common, particularly in women aged 40-60. Although larger cysts can sometimes be felt as “lumps”, many cysts are undetectable by physical examination.

Cysts are frequently seen as abnormal shadows on mammograms. They are usually seen as discrete lesions with well-defined or partially well-defined, partially obscured margins. They vary from round to oval in shape. They are seen as intermediate density or high density lesions. When a cyst is suspected, breast ultrasound examination is usually performed. Breast ultrasound is the most sensitive and accurate method for the identification and diagnosis of breast cysts. With modern ultrasound equipment accuracy rate of 95% to 100% can be expected.

PHYLLOIDES TUMOR

Phylloides tumor is a rare fibroepithelial breast tumor that occasionally has unpredictable clinical behaviour. They generally present as large masses with sudden rapid growth. On mammography they are seen as well-defined masses, may or may not show lobulations and are usually covering the entire breast.

FIBROCYSTIC DISEASE

Fibrocystic breast condition is a common, non-cancerous condition that affects more than 50% of women at some point in their lives. The most common signs of fibrocystic breasts include lumpiness, tenderness, cysts (packets of fluid), areas of thickening, fibrosis (scar-like connective tissue), and breast pain. Having fibrocystic breasts in itself is not a risk factor for breast cancer. Fibrocystic disease is seen as diffuse heterogeneous lesions in dense breasts. Few lesions could be seen as discrete intermediate density lesion on mammography corresponding to cystic changes as seen on gray scale ultrasonography.Multiple coarse calcifications may be seen as associated findings.

GALACTOCELE

A galactocele is a cystic tumor containing milk or a milky substance that is usually located in the mammary glands. It can be caused by an infection or is seen in postpartum period in lactating females. Galactocele presents as a discrete mass, round to oval in shape with partially well defined partially obscured margins and may show evidence of coarse calcifications.

BREAST ABSCESS

Patients with acute breast abscess are usually not taken up for mammography since it is a very painful condition. But when performed they have a diffusely increased density or may show irregularity in shape and ill-defined margins. These are high density lesions associated with skin thickening and architectural distortion and are common mimickers of malignancy on imaging. A chronic recurring breast abscess in Indian setting should raise suspicion for tubercular etiology.

CARCINOMA BREAST

Breast cancer is a heterogeneous disease in terms of its clinical course, gross and microscopic pathology, and imaging characteristics. Several histologic classifications exist. One example is the World Health Organization (WHO) classification, which divides breast cancers into noninvasive type (in situ), invasive type, and Paget disease of the nipple. In situ carcinoma is characterized by growth within the ducts without penetration of the basement membrane. It is subdivided into ‘ductal carcinoma in situ’ (DCIS) and ‘lobular carcinoma in situ’ (LCIS). Invasive carcinoma denotes neoplastic penetration of the basement membrane of a duct containing DCIS and extension of neoplastic cell aggregates into the mammary stroma. It is further subdivided into these types: ductal, which accounts for about 75% of all invasive breast cancers; medullary; mucinous, or colloid; papillary; tubular; adenoid cystic carcinoma; and carcinoma with metaplasia. Paget disease of the nipple is a type of breast cancer that starts in the breast.

Mammography is unchallenged as a screening test for the early detection of breast cancer. No other imaging technique matches its ability to find small cancers. Some of these criteria are extensively accurate. They are divided into major signs of malignancy (conventional signs) and supporting signs of malignancy (indirect signs).

Major Signs:

1. Spiculated Margins

Spiculated margins are a true diagnostic feature of malignancy. Strands of tissue are seen radiating out from an illdefined mass, producing a stellate appearance This appearance is pathognomonic of breast cancer. Spiculations represent retraction of tissue strands towards the tumor due to fibrosis - as a result of desmoplastic response. Sometimes, only the spiculation are seen.

2. Clustered Microcalcifications

Mammography is the only technique capable of detecting microcalcification. Microcalcificaitons, even when found in isolation, herald the presence of early stage breast cancer. Five or more calcifications, measuring less than 1mm, in a volume of one cubic centimeter, define a ‘cluster’. The possibility of malignancy increases as the size of individual calcification decreases, the total number of calcification per limit area increases. It is the distribution and morphology of the calcifications, which defines their significance.

Supporting Signs of Malignancy

These indirect signs, though nonspecific, signify enough risk to warrant intervention.

1) Poorly Defined Mass

Most breast cancers are seen as poorly defined masses, without any mammographic features more suggestive of malignancy. Circumscribed masses with margins that are mostly well-defined with only an ill-defined portion are also managed as other ill-defined masses. There is a sizable number of benign breast masses whose margin appears to be poorly defined, and therefore are difficult to differentiate from malignancy resulting in the need to biopsy in order to detect early cancer.

2) Microlobulation

Lobulations are usually associated with fibroadenomas. Increased number of lobulations, measuring few millimeters, should be suspected for malignancy.

3) Architectural Distortion

Breast cancer does not always produce a mammographically visible mass. Sometimes it produces just a localized cicatrization. If previous surgery and trauma to the breast can be excluded, there is a high likelihood that the distortion is because of malignancy. Invasive carcinoma distorts the interface between breast and normal parenchyma due to desmoplastic response of host tissue to the malignancy.

4) Asymmetric Density

Asymmetric density is the three dimensional area in which the density is greatest at the centre and fades towards the periphery trying to form a mass. In this situation, it is helpful to view the mammograms of both breasts side by side.

5) Nipple Retraction

Nipple retraction “over a short period of time” is suspicious of an underlying cancer.

6) Enlarged Axillary Lymph nodes

Demonstration of large nodes is nonspecific sign of malignancy. Involvement of the nodes(s) indicates worsening of prognosis.

References

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Fibroadenoma
Fig.1 Fibroadenoma. Mammogram showing round intermediate density lesion with well defined margins
Multiple breast cysts
Fig.7 Multiple breast cysts. Mammogram showing retroareolar intermediate density masses; one of them is showing partial ‘halo sign’.
Involuting Fibroadenoma
Fig.2 Involuting Fibroadenoma.Mammogram showing coarse calcifications in an involuting fibroadenoma
Phyllodes tumour
Fig.8 Phyllodes tumour.CC View showing large lobulated mass covering the entire left breast.
Multiple fibroadenomas
Fig.3 Multiple fibroadenomas.Cranio-caudal view showing multiple fibroadenomas of variable densities
Invasive Ductal Carcinoma
Fig.9 Invasive Ductal Carcinoma showing microlobulated borders and microcalcifications
Multiple Fibroadenomas
Fig.4 Multiple Fibroadenomas. Medio-lateral oblique showing multiple fibroadenomas extending up to axillary region
Invasive Lobular Carcinoma
Fig.10 Invasive Lobular Carcinoma appearing as B/L spiculated masses.Lesion in the right breast infiltrated through the skin leading to a fungating mass; seen as high density lesion in the region of right axillary tail.
B/L Breast abscess
Fig.5 B/L Breast abscess.MLO view showing retroareolar ill-defined high density lesions in B/L breasts.
Invasive Ductal Carcinoma
Fig.11 Invasive Ductal Carcinoma seen as high density spiculated mass in left breast.
Galactocele
Fig.6 Galactocele. Mammogram showing calcified galactocele
Non Hodgkin Lymphoma
Fig. 12 Non Hodgkin Lymphoma appearing as well circumscribed high density spherical nodes.
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