Mammography is a particular type of imaging which use an x-ray system, which has a low-dose for the purpose of detecting breast cancer at a very early stage. But even with the help of Mammography, in 10-30% cases of breast cancers would be missed. By way of this paper an attempt has been made to understand the factors, which cause for missed breast cancers, and discuss ways to reduce the false negative rate of mammography.
The false negative rate of mammography was around 8-10% according to the data of the Breast Cancer Detection Demonstration project. Another study was of the opinion that the rate of missed breast cancers with regard to mammography was very high as 35%. (Harvey, Fajardo, Lnnis, 1993) In another study of 10 radiologists the true cases of cancers were considered to be in 74-96% cases which were understood after analyzing 150 mammograms. (Elmore, Wells, Lee, et al. 1994) Alternative imaging modalities have been recommended for the purpose of detecting and diagnosing Breast carcinoma by way of recent studies held in this field. These include magnetic resonance (MR), ultrasonography (U.S.), studies of nuclear medicine and imaging. The high quality of mammography, which is done with utmost attention giving importance to position and detail, would be able to greatly increase the efficiency in interpreting images.
The factors which cause for missed breast cancers are poor position or the poor quality of technique employed, due to dense parenchyma that makes a lesion unclear or unexplained, (Patel, Whitman, 1998) when lesion is located outside the vision of viewing, lack of understanding about the depth of an abnormality, the suspect which is found is wrongly judged, characteristics of malignancy are subtle, or the malignancy is changing, but slowly. When their appearance shows a benign cause or when their appearance suggests distortions or would suggest areas of asymmetry, breast cancers would be missed. (Burrel, Sibbering, Wilson, et al. 1996) In a study conducted on screening mammography, it was found that out of 320 cases, 77 were missed, which made a case of 24% due to the cause of dense breasts and density which was developing which was not to be found by the radiologists. (Bird, Wallace, Yankaskas, 1992) In yet another study conducted it was found that another factor of observer misjudgment was the cause of missed breast cancer in 10 out of 94 cases studied, while it was subtle signs of malignancy, which caused missed breast cancer in 21 out of 94 cases. (Ikeda, Anderson, Wattsgard, et al. 1992)
One of the important causes of missed breast cancers are due to dense parenchyma. Breast parenchyma, which is dense, makes a compromise on the ability to detect a mass. This mass is usually a lesion, which is non-distorting and is non-classified. In finding out micro calcifications, which are dim, or in finding out areas, which have architectural distortion, radiologists have to be extremely cautious. The tissue must be analyzed thoroughly for finding out the disruption, if any caused of the normal elements of parenchyma. This is because in a dense breast, architectural distortion would be only signs of malignancy. This area of architectural distortion should be undertaken for further studies to find out more on this aspect, if it is not considered as a post-surgical scar. In order to understand the presence of the solid mass in relation to the architectural area of distortion, ultrasonography (U.S.) may prove to be beneficial. U.S. are of great usage for negative findings related to mammography- in analyzing abnormalities related to mammography and thus can be useful for anyone having dense breast parenchyma.
In all matters relating to radiology, image contrast and proper position are of great importance. But they hold their utmost importance in mammography. For the purpose of maximizing the quantity of tissue, which is included on the image, the radiologist must conform to the standards of positioning. (Hendrick, Basett, Botsco, et al. 1999) It is essential that positioning be creative and strict as much as possible, in order to understand those areas, which have palpable abnormalities on the images. If the positioning is creative, it proves to be of great benefit to patients who have suffered a stroke, those who are tensed up, who have shoulder problems or other factors, which affect the visualization of the posterior breasts on standard mediolateral oblique views. Again the technologist in order to avoid attaining over-penetrated or under-penetrated images must optimize image contrast. For optimal density on the image, it is essential that the photocell be properly positioned. In order to optimize contrast image, daily processor quality control should be given proper importance. To understand whether the imaging technique used is sufficient, it is essential that the images should be reviewed under correct mammographic viewing conditions.
Two of the main causes which lead to missed breast cancer are due to the wrongs committed by the radiologist. The first cause of error of the radiologist is due to lack of perception. The radiologist commits such a wrong when lesion happens to be included in the area of the vision. Such an error is evident, but is not identified by the radiologist. The lesion would either display the characteristics of malignancy, which are subtle or it may not exhibit these characteristics, which cause for its less visibility. The faint microclacifications, small masses that are nonspiculated, areas of architectural distortion, would all be in a difficult position to perceive. In order to avoid this problem of perception error, what can be done is that the images could be reviewed as images of mirror with the help of mediolateral oblique images and craniocraudal images placed together. What the radiologist has to do is to compare those areas, which are like-areas, on the side-by-side images. This would be helpful in identifying mass, which has low-density, and any other focal asymmetric density.
The treatment of a patient can be affected directly when the radiologist fails to identify multicentric and multifocus breast cancers. Multicentric breast cancer is defined as two or more cancers in different quadrants. Multifocus breast cancer on the other hand is defined as two or more cancers in the same quadrant. Breast conservation therapy is constricted in the case of Multicentric breast cancer. The radiologist would not look carefully for other lesions- because of the satisfaction of search, in which the findings of a search would enable the radiologist not to look out for other lesions. It is essential that after the findings of suspect lesion, radiologist must pay special attention to the contralateral breast. This is because of the reason that contralateral synchronous cancers have been reported in 0.19%-2.0% of patients (Kinnie, 1987)). It could also be seen at MR imaging in 9%-10% of the patients. In cases where there have been has been obvious that it would be benign lesion with a subtle cancer, satisfaction of search was supposed to happen. But what the radiologist has to do is not to be satisfied with a single lesion. There should be attempt to find out other lesion-either benign or malign and the radiologist should not be satisfied with a single lesion, which has been found out.
In the case of primary breast cancer, it would not be either observed or would be very subtle and may be occult at mammography. It is essential that care should be devoted to focal asymmetric densities or abnormalities in mirror image. This is extremely important in identifying the lesion, which is primary. When the findings of mammography have proved to be negative, MR imaging has been found to be extremely helpful in analyzing the primary carcinoma. On the other hand, in patients having no obvious breast lesion or having multi-centric cancer, U.S. has been found to be really helpful, in the search for occult breast malignancy. (Khalkhali, Vargas 2001) (Orel, 2000) Researchers have found U.S. To be complementary to mammography, in those patients who were found to have known breast cancers and had planned breast conversation. For showing the local reach of the breast cancer, MR imaging is becoming extremely important in those patients.
Yet another major cause of missed breast cancer is which is related to the error on the part of a radiologist is the wrong interpretation of a lesion. Such a misinterpretation occurs on the part of a radiologist when an abnormality, which has suspect features, is misinterpreted as having definite features or at least probably being benign. The factors, which cause misinterpretation on the part of a radiologist, are fatigue, lack of experience or lack of proper attention. The wrong interpretation could also be due to the fact, that a lesion has been growing slowly, that the radiologist was not able to gather all the features necessary to understand the features of the lesion, or because the prior images were not used for the purpose of comparison. As a result, the radiologist would commit the mistake of wrongly judging the abnormality of the breasts by it benign characteristics and would thereby not focus by missing the most…