Carcinoma Breast

In addition to the architectural information, there are features related to the time course of enhancement that are predictive of cancer.The most robust and reproducible features relate to the qualitative assessment of the enhancement curve. The enhancement curve is not measured as the average enhancement curve over the lesion. Rather, the enhancement curve should be sampled from multiple locations in the lesion, and the most suspicious enhancement curve in the lesion should be assigned to the lesion. Enhancement curves can be divided into three major types: persistent, plateau, and washout. Persistent enhancing curves demonstrate continued enhancement beyond the first 2 minutes of acquisition. Plateau curves will plateau and level off after 2 minutes of contrast injection. Washout curves will reach a peak after 2 minutes of contrast injection and new signal intensity area may be seen in addtion to already diagnosed malignant area. Washout is felt to be a feature suspicious for cancer, plateau is felt to be indeterminate, and persistent enhancement is reported to be a feature most consistent with benignity. These features are not 100% accurate , and reported accuracies  vary. This is particularly true in nonfocal mass enhancement in which persistent enhancement does not exclude malignancy. Similarly, classic fibroadenomas can demonstrate washout and this should not be used as evidence of malignancy. Use of MR imaging demonstrats additional foci of cancer that are mammographically occult in up to 40% of women undergoing mastectomy for breast cancer. 

Breast cancer is the second leading cause of cancer deaths among women. Imaging plays a crucial role in all aspects of breast cancer care. This includes early detection through screening, diagnosis and associated image-guided biopsy, treatment planning, and follow-up.The limitations of x-ray mammography have led to extensive efforts to develop complimentary imaging techniques to improve breast imaging performance,particularly in the radiographically dense breast. The most accepted adjunct modality is breast sonography, which is now widely used in the diagnostic evaluation of women with abnormal screening mammography or clinical examination.

Inspite of advances in other imaging modalities, Mammography remains a  sensitive method for detecting early breast cancer, and it is also the most practical investigation for screening . Although general rules for differentiation between malignant and benign lesions exist, in clinical practice only 15%–30% of patients referred for biopsy are found to have a malignancy.The analysis of a mass seen on mammography is a complex process involving assessment of its size, shape, border characteristics,and density.Primary signs of malignant breast lesions on Mammography are density of mass which is more than the rest of breast,and  outline of malignant mass which is speculated or irregular (caused due to infiltrative duct carcinoma and invasive lobular carcinoma also called as speculated carcinoma).Occassionally well defined smooth  border mass( is caused due to  medullary, colloid and papillary/intracystic carcinoma, and this entity is called as circumscribed carcinoma) may be seen. Mammographic size of mass is always less than the palpable mass. Microcalcifications are seen in upto 40% of cases of cancer and  20% of clustered microcalcifications represent malignancy. In addition to these signs other primary signs on mammography are architectural distortion, asymmetric density (distinct dense tumour mass seen with in the asymtric density) and segmental enlargement of the duct.
Secondary signs of breast malignancy are skin changes in form of retraction, thickening, dimpling, Nipple/ areola retraction, nipple discharge, eczematoid changes of nipple/areola in duct carcinoma (Paget’s disease), increased vascularity and axillary lymphadenopathy.

 
Sonographic characteristics of benign lesions are smooth well defined margins, Anechoic or hypoechoic echogenicity of lesion, no internal echo pattern or homogenous echopattern, no retrotumoral acoustic phenomenon or no posterior enhancement, variable compressibility, and ratio of lateral/ anteroposterior dimension ( more than one), whereas the features of malignant lesions are irregular, indistinct margins, variable echogenicity, heterogenous internal echopattern, irregular posterior shadowing, no compressibility and and ratio of lateral/ anteroposterior dimension ( less than one).In addition there are lesions which do not have characteristic features of either benign or malignant lesions,  and therefore  are termed as indeterminate lesions.

On MR Imaging , the initial approach to enhancement of breast is to make a determination of whether the enhancement represents a focal mass or not a focal mass.  In order to define which of these masses are malignant and which are benign, other architectural features can be utilized. An important feature is the shape and border of the lesion .The more irregular or spiculated the lesion margin is, the more likely it is to be cancer.Lesion borders that are smooth or demonstrate gentle lobulations are more likely to be benign. This distinction is still not 100% accurate. There are lobulated-bordered cancers; for example, colloid, tubular, and medullary cancers can have well-defined lobulated borders. In addition, benign lesions such as radial scars can demonstrate spiculation. Other features can be valuable in further distinguishing between benign and malignant enhancing focal masses. Rim enhancement of the lesion is highly suggestive of malignancy. Cystic lesions in the breast will typically have an enhancing rim. The smooth enhancing rim of a cystic lesion does not suggest any evidence of malignancy. It is seen that enhancing rims in solid lesions can occur not only at the periphery of the lesion, but occasionally can be seen entering the internal portion of a lesion.The finding of septations within a lobulated or smooth-bordered lesion should be considered as good evidence of benignity.
Although fibroadenomas in young women may be edematous and bright on T2-weighted images, they hyalinize over time. Hyalinized fibroadenomas tend to be low signal on T2-weighted images. Although cancers can occasionally be low signal, this is usually due to extensive desmoplastic reaction and is associated with a spiculated lesion. A smooth border or lobulated lesion that is low signal on T2 will almost certainly represent a hyalinized fibroadenoma. These hyalinized fibroadenomas may enhance or may eventually lose their blood supply and stop enhancing.The two main important factors to be determined are the distribution of the enhancement and the form of the enhancement. If the distribution resembles the distribution of breast ducts, it is more likely to be cancer. Distributions can be described as ductal, segmental, regional, or diffuse.  The size of the foci that make up the area of enhancement is also referred. The descriptions include stippled, clumped, inhomogeneous, and confluent enhancement. Therefore, using these characteristics, stippled enhancement in a regional or diffuse distribution most likely will be benign, and confluent or clumped enhancement in a segmental distribution most likely will be malignant. Lesions identified as nonfocal mass enhancement most often will include a significant fraction of in situ cancer; however, there may be associated invasion.