- Dr. Edward Jankhe
- Department of Radiology
- Providence Saint Joseph Medical Center, Burbank, CA
TABLE OF CONTENTS
- 1. Mammography: The
Technique
- 2. Guidelines
- 3. Definitions of
Mammographic Lesions
- 4. Benign
Mammographic Lesions
- 5.
Suspicious Mammographic Lesions
- 6. Exposure
Risks
|
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Excluding skin cancer and in situ carcinomas, breast cancer is the most common cancer
occurring in females, with a lifetime incidence of about 12.6% ( 1 in 8). It is also the
second most common cause of cancer death in females. The American Cancer Society estimates
that in 1997 there will be 181,600 new cases of breast cancer in females, and an estimated
43,900 women will die from breast cancer. Breast cancer develops over a period of years,
and controlled medical studies have show that if it is detected in a localized stage,
without spread to regional lymph nodes, the 5 year survival is about 97%. However, when
the cancer has spread to axillary lymph nodes the 5 year survival decreases to about 76%,
while the 5 year survival decreases further to about 20% with distant metastases to the
lung, bone marrow, liver or brain. This improved survival with early detection is the
rational for breast imaging and screening mammography in particular. Breast imaging and
mammography also play a role in defining the extent and nature of palpable abnormalities,
or the presence of additional occult disease in cases of clinically evident abnormality
and prior to therapeutic intervention. |
MAMMOGRAPHY: THE TECHNIQUE
Mammography refers to breast imaging with the use of x-rays. The x-ray images are
produced by the attenuation (absorption) and scattering of the x-ray beam by the various
breast tissues before the beam reaches and exposes the film. The first reported use of
X-rays to demonstrate breast cancer was in 1913, by Dr. Albert Solomon who obtained
radiographs of gross anatomic mastectomy specimens. Over the subsequent 70+ years the
technique has been developed and refined through the use of dedicated units, compression,
molybdenum targets, standardized techniques, moveable grids, automatic exposure control,
high resolution films, rare earth screens, automatic film processing and ever greater
attention to quality control. Dedicated mammographic units are currently sold by multiple
vendors with generally minor differences in technical specifications.
Currently mammography is performed with a dedicated mammography unit, to optimize
radiographic exposure and breast compression; and with rigorously controlled film
processing and development to optimize image quality. Because the x-ray images depend on
differential attenuation of the x-ray beam by the different breast tissues, if may be
difficult to separate normal functioning breast tissue from a benign or malignant mass. As
a consequence mammography is less sensitive in dense breasts than in fatty, involution
breasts.
Both screening and diagnostic mammograms routinely start with
the standard mediolateral oblique and craniocaudal projections. For further evaluation of
suspected abnormalities supplemental views including exaggerated craniocaulal, spot
compression, magnification, vertical lateral, tangential, and push-back views may be
obtained.
The spot compression view, with or without magnification, is
used to separate a suspected density from adjacent parenchyma and better define its
margins. Spot compression magnification views also better define the presence and
morphology of various breast calcifications and masses.
Tangential views are useful to define the relationship of a
parenchymal density or calcifications to the skin.
Vertical lateral views better define the anatomic location of
lesions within the breast as well as demonstrate the presence of Milk-of -calcium (
calcium precipitate) within small cysts.
Push-back (Ekland) views allow improved imaging of breast tissue anterior
to breast prostheses.
Comparison to old studies is also useful for evaluation of
stability or interval change.
MAMMOGRAPHY: GUIDELINES
Based on review and discussions of the available scientific evidence, The American
Cancer Society recently changes it’s recommended guidelines for screening mammography
to include yearly screening for all women 40 years of age and older. Previously the
recommendation had been for screening mammography every 1-2 years.
The current guidelines are:
| American Cancer Society
Recommendations for Breast Cancer Detection in Asymptomatic Women (March 23, 1997) |
| 20-40 Years of Age |
- Beast self examination monthly
- Breast clinical examination by a healthcare professional every 3 years,
- No recommended Mammography
|
| 40 and Older |
- Breast self examination monthly,
- Breast clinical examination by a healthcare professional very 3 years,
- Mammography every year
|
| Cessation of annual screening is not considered to be age-dependent,
but a function of co-morbidity; and no termination age was specified. |
DEFINITION OF
MAMMOGRAPHIC LESIONS
The sensitivity of mammography is initially determined by the relative background
composition of the breast parenchyma. The denser the breast the less sensitive it is to
the detection of small masses, although small calcifications can generally still be
detected. The mammograms are initially evaluated for the presence of masses, architectural
distortion, asymmetric parenchyma, calcifications and skin changes. These mammographic
findings are then further characterized and compared to old studies, if available.
Mammographicaly a mass is defined as a space occupying
lesion seen in two different projections, with density
defined as a collection seen in only one view. A mass is then further characterized by
it’s shape, margins, density, size, orientation and presence of associated
calcifications.
- Shape is a generally nonspecific characteristic, both benign and
malignant masses tend to develop in one spot and grow circumferentially. An irregular
shape is more concerning as its suggests indistinct or irregular margins. Some skins
lesions, warts and seborreic keratoses, have typical appearances due to the variegated
surfaces and occasionally radiolucent/air halo. Some intramammary nodes have a typical
reniform configuration with a fatty notch.
- Margin or contour analysis characterizes the transition zone from mass to
surrounding parenchyma or fatty tissue. The significance arises from the tendency of
invasive carcinoma to infiltrate adjacent tissue and have indistinct, microlobulated or
frankly spiculated margins.
- Well circumscribed or sharply marginated masses, either with or without a
radiolucent halo, are probably benign. If all margins remain sharply circumscribed on
magnification views , and there is no associated suspicious calcification, 98% to 99% will
be benign with a differential of fibroadenoma, cyst or intramammary lumph node. When
initially found ultrasound to exclude a cyst is a very useful adjuvant study. If the
lesion is solid on ultrasound, serial six month mammograms for two years would be
suggested, because of the low, 1-2%, incidence of malignancy. An alternative to serial
imaging would be FNA or core needle biopsy.
- Circumscribed masses with irregular or microlobulated margins on
magnification views should be considered suspicious and biopsy suggested.
Similarly if the margins remain indistinct or ill-defined on additional special views
the lesion must be considered suspicious and biopsy considered.
- Masses with spiculated margins are suggestive of malignancy.
With cancer, the spicules represent finger-like projections of the malignant cells.
Other spiculated densities may represent radial scar/sclerosising adenosis but are still
suspicious and can be associated with tubular carcinoma. A spiculated density may also be
secondary to a post operative scar, although the clinical history should provide the clue
and subsequent serial follow up should demonstrate maturation and involution or at least
stability of the scar.
- Density describes the relative attenuation of a breast lesion compared to
the normal fibroglandular tissue of the breast. Cancer is frequently, but not always
higher in density than surrounding parenchyma, and can be isodense or rarely lower in
density. Fat containing/radiolucent masses most frequently represent oil cysts, lipoma,
galactocele, hamartoma or fibrolipoma, and are considered benign unless other
characteristics are suspicious.
- Calcifications can occur in the breast from many causes and be associated
with both benign and malignant conditions. Many benign calcifications have a typical
appearance but some may be indeterminate or simulate malignant calcifications. Suspicious
calcifications occur in about one-third of breast cancers, and may develop before the
invasive phase. Some benign type calcifications have a typical appearance, while others
are more nonspecific but are usually larger, and coarser than the suspicious
calcifications. The pattern of distribution may also be helpful in evaluating the
calcifications, with clustered, segmental and fine linear or branching patterns being more
suspicious.
MAMMOGRAPHIC
LESIONS: TYPICALLY BENIGN
- Skin calcifications are typically small round to oval with
lucent centers.
- Vascular calcification is similar to elsewhere in the body and
forms contiguous or interrupted dense paired tubular lines.
- Coarse or popcorn like calcification can be seen in an
involuting fibroadenoma.
- The large rod shaped calcification of secratory disease/plasma cell mastitis
are usually over 1mm in diameter, may have lucent centers and occasionally branch.
- Small, dense rounded calcifications are usually considered
benign and related to involution.
- Milk of calcium is benign and represents calcium precipitate in
small cysts.
- Eggshell calcifications are benign
- Small amorphous, indistinct, hazy rounded and flake like calcifications
may be associated with both benign and malignant process and are of intermediate concern.
MAMMOGRAPHIC
LESIONS: HIGH PROBABILITY OF MALIGNANCY
- Pleomorphic or heterogeneous (granular) fine linear and/or branching calcifications.
EXPOSURE RISKS
FOR MAMMOGRAPHIC STUDIES
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