In 1995 the Norwegian Government initiated an organized population-based service screening program [10], in which mammography results and interval cancer cases are carefully registered by the Cancer Registry of Norway. The Norwegian Breast Cancer Screening Program (NBCSP) originally included four counties. Other counties were subsequently included, and by 2004 the screening program achieved nationwide coverage. All women between 50 and 69 years of age receive a written invitation biannually, and two-view mammograms from participating women are independently evaluated by two readers.
Since larger tumors are easier to detect on mammograms than smaller tumors, the STS was modeled as an increasing function of the tumor size, X, in millimeters. As used for the tumor growth curve, a variant of the logistic function was used for the STS. Mathematically, the modeled STS, S(X), can be written as:
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Since mammography screening detects a higher proportion of the larger prevalent tumors compared with the smaller prevalent tumors, the pool of undiagnosed tumors is expected to have a clear overrepresentation of small tumors shortly after screening. One would suspect this could lead to relatively small tumors detected shortly after screening, followed by gradually increasing tumor sizes with the time since last screening. This trend is severely damped, however, as each tumor before detection must reach a certain individual size to produce sufficient symptoms to alarm the woman. In practice, the relationship between tumor size and clinical detection results in only a vague trend in interval cancer tumor sizes by time since screening (correlation = 0.01 in the NBCSP), whereas the number of interval cancers increases sharply. We have therefore chosen to disregard the size distribution of interval cancers, and build our estimation procedure on the observed frequency of interval cancers by the time since screening, the number of cases found at screening, the tumor size distribution of screening cancers, the assumed background incidence, and the size distribution of clinical tumors without screening (based on historical data).
The mammography STS was estimated to increase sharply from around 2 mm to 12 mm, with the STS reaching 26% at 5 mm and 91% at 10 mm (Figure 4b). There was no significant difference in the estimated STS between the two age groups (P = 0.83 for the STS at 5 mm).
Whereas screening with mammography has been related to reduced mortality in several randomized trials [32, 38], so-called overdiagnosis remains a controversial topic. Following the conservative definition of the number of overdiagnosed cases as 'the number of women who would not had breast cancer in their life time without participating in mammography screening', our new model can be used to estimate the level of overdiagnosis under different screening designs. As a motivation for further studies, we have estimated the probable age at which screening-detected cancers would have become clinically detected without screening, given one screening examination at different ages. Figure 6 illustrates why screening in higher age groups is controversial, since a large proportion of cancers would never have surfaced in the absence of screening. On the other hand, our estimates indicate that the vast majority of screening cancers in the current NBCSP age group (50 to 69 years) would at one stage been detected clinically without screening. The new method presented here provides a toolbox for estimating this and other central issues related to mammography screening.
A mammogram is an x-ray picture of the breast. Health care providers use mammograms to look for early signs of breast cancer. There are two types of mammograms: screening mammograms and diagnostic mammograms.
A screening mammogram is a mammogram usually done for women who have no signs or symptoms of breast cancer. Regular screening mammograms can help reduce the number of deaths from breast cancer among women ages 40 to 74. This is because they can find breast cancer early and treatment can start earlier, maybe before it has spread.
But screening mammograms can also have risks. They can sometimes find something that looks abnormal but isn't cancer. This leads to further testing and can cause you anxiety. Sometimes mammograms can miss cancer when it is there. It also exposes you to radiation. You should talk to your provider about the benefits and drawbacks of mammograms. Together, you can decide when to start and how often to have a mammogram.
A diagnostic mammogram is done for people who have a lump or other signs or symptoms of breast cancer. The signs can include breast pain, thickening of the skin of the breast, nipple discharge, or a change in breast size or shape. But these signs can also be caused by a breast condition that is benign (not cancer). A mammogram, along with other tests, can help your provider figure out whether you have cancer.
When you have a mammogram, you stand in front of an x-ray machine. The person who takes the x-rays places your breast between two plastic plates. The plates press your breast and make it flat. This may be uncomfortable, but it helps get a clear picture.
You will get both breasts x-rayed from the front and from the side. Afterwards, a radiologist (a doctor with special training) will read the mammogram. The doctor will look at the x-ray for early signs of breast cancer or other problems. You will usually get the results within a few weeks, although it depends on the clinic or medical office that you went to. If your results are not normal, you should hear back earlier. Contact your provider or the office where you had the mammogram if you do not receive a report of your results within 30 days.
An abnormal (not normal) mammogram does not always mean that there is cancer. You will need to have additional mammograms, tests, or exams before your provider can tell for sure. You may also be referred to a breast specialist or a surgeon. But it does not necessarily mean you have cancer or need surgery. You would see one of these doctors because they are experts in diagnosing breast problems.
In many states, women whose mammograms show heterogeneously dense or extremely dense breasts (which includes about half of all women) must be told that they have dense breasts in the summary of the mammogram report that is sent to patients (sometimes called the lay summary).
Kerlikowske K, Ichikawa L, Miglioretti DL, et al. Longitudinal measurement of clinical mammographic breast density to improve estimation of breast cancer risk. J Natl Cancer Inst. 2007;99(5):386-395.
Venkataraman S, Slanetz PJ, Lee CI. Breast imaging for cancer screening: Mammography and ultrasonography. UpToDate. 2021. Accessed at -imaging-for-cancer-screening-mammography-and-ultrasonography on October 1, 2021.
BreastScreen Aotearoa is a free national breast screening programme that checks women for early breast cancer. Describes in simplified Chinese what happens after you have had a mammogram. For BreastScreen Aotearoa Centres only.
Breast screening information in English for women under 45 years of age who are not yet eligible for free mammograms from BreastScreen Aotearoa. BreastScreen Aotearoa is a free national breast screening programme that checks women aged 45-69 for early breast cancer.
Research shows that mammograms are not as good at detecting breast cancers and saving lives in younger women, particularly before the menopause. While mammograms can detect cancer in your age group, there are some drawbacks to having mammograms if you are under 45. In this age group, breast tissue may be denser. This makes the mammogram harder to read, and cancers are more likely to be missed. As well as this, women under 45 are more likely to have something show up on their mammogram that needs checking but turns out not to be cancer. For further information on the harms and benefits of screening in young women visit www.breastscreen.govt.nz
Some women under 45 years who are at a greater than average risk of getting breast cancer and do not already have a breast problem or symptom can have free mammograms at a public hospital if they have one (or more) of the following:
It is important for all women (whether or not they are having mammograms) to get to know what their breasts are like normally. If you feel or notice anything that is not usual for you, have it checked by your doctor.
You may have just received an abnormal mammogram result, or perhaps you or your health care provider found a breast lump or other breast change. Keep in mind that breast changes are very common, and most are not cancer. This page can help you learn about symptoms during your lifetime that are not cancer as well as follow-up tests used to diagnose breast conditions and treatments for specific breast conditions.
MRI (also called Magnetic Resonance Imaging): A procedure that uses a powerful magnet, radio waves, and a computer to take detailed pictures of areas inside the breast. An MRI can be used to learn more about breast lumps or large lymph nodes that were found during a clinical breast exam or breast self-exam but were not seen on a mammogram or ultrasound.
Malignant transformations in the epithelial components of fibroadenomas are generally considered rare. The incidence of a carcinoma evolving within a fibroadenoma was reported to be 0.002% to 0.0125%.42, 43 About 50% of these tumors were lobular carcinoma in situ (LCIS), 20% were infiltrating lobular carcinoma, 20% were ductal carcinoma in situ (DCIS), and the remaining 10% were infiltrating ductal carcinoma. The clinical, sonographic and mammographic findings are usually similar to those of benign fibroadenomas,44, 45 and the malignant changes are often noted only when the fibroadenoma is excised. 2ff7e9595c
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