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USG of the breast is now an established modality. It is used in the characterisation of focal breast lesions as well as in the primary evaluation of mammographically dense breasts. It helps guide biopsies as well. We present a pictorial essay on the role of USG in various breast pathologies
USG has come a long way from being a modality used by the military for detecting flaws in metal to its present status, where high-resolution scans even help us differentiate benign from malignant breast disease.
It is advisable to perform a targeted breast USG whenever there is a palpable or focal mammographic abnormality in the breast. Although USG is not efficacious as a screening modality, combined mammography and USG pick up more cancers than mammography alone.
For USG examination of the breast, a linear-array transducer of at least 7 MHz frequency is required with a machine that has good spatial and contrast resolution. The patient is scanned in the supine position and then in the contralateral oblique position for the axillary and upper outer quadrants. Color Doppler is not very effective but three-dimensional coronal imaging, as well as elastography, may help to avoid unnecessary biopsies in benign-appearing lesions.
Reporting of the USG and mammography findings is facilitated with the breast imaging reporting and data system (BIRADS) proposed by the American College of Radiology (ACR), which is available at www.acr.org and in some articles.
The prepubertal breast has only minimal duct development around the nipples. Sometimes this may be asymmetric and may mimic a subareolar mass (similar to gynecomastia in males). This is called premature asymmetric ripening. It is very important to recognize it because if it is surgically excised by mistake, there will be no breast development on the operated side. The findings are identical to those of asymmetric gynecomastia in males.
The breast has alternate hyperechoic and hypoechoic layers as follows:
Cooper's ligaments are echogenic bands that suspend the breast from the superficial layer of the superficial fascia.
The coronal breast plane is never seen on routine 2D USG. Benign lesions show a compression pattern, whereas malignant lesions show a retraction pattern.
Simple cysts in the breast are completely anechoic, with a thin echogenic capsule, posterior enhancement, and thin edge shadowing [Figure 4A]. Complex cysts have intracystic echoes, septae or thick walls, and may be seen in clusters [Figure 4B]. Although this is rare, we have seen a case of breast cysticercosis in a patient who also had a cysticercus granuloma in the biceps tendon [Figure [Figure4C4C,,D].D]. A significant number of complex cysts, especially those with a solid intracystic mass, may be malignant.
Papillomas in the breast may be intracystic [Figure 5A] or intraductal [Figure 5B]. They are difficult to differentiate from papillary carcinomas and a biopsy is required for the same. Intraductal papillomas are the most frequent cause of a bloody nipple discharge.
Fibroadenoma is the most common benign tumor in the breast and is usually seen in young women. It may increase in size during adolescence or pregnancy and lactation, and undergo atrophic changes after menopause. It is usually homogenous, well-circumscribed, hypoechoic, ellipsoid, wider than tall, and may even show posterior enhancement on USG [Figure 6A]. It may undergo calcific degeneration. The calcifications within a fibroadenoma are coarse and may show posterior shadowing [Figure 6B]. Complex fibroadenomas, that is, fibroadenomas with epithelial calcifications, papillary apocrine metaplasia, sclerosing adenosis, and cysts larger than 3 mm, have a higher incidence of transformation into breast cancer.
These are rapidly growing, benign-looking lesions with cleft-like cystic spaces and are moderately vascular on USG. They are fibroepithelial tumors that may be benign or malignant. They tend to recur and may rarely metastasize.
Acute abscesses may occur during lactation and are clinically evident [Figure 8A]. In our country, chronic abscesses may be due to tuberculosis and may present as breast lumps with discharging sinuses [Figure 8B].
Edema of the breast can occur following surgery or radiation. It may also occur due to lymphatic or venous obstruction [Figure 9].
This is a benign complex lesion of sclerosing adenosis that appears spiculated on mammography [Figure 10A] and may show a retraction pattern on 3D coronal USG [Figure 10B]. It is usually ill-defined and hypoechoic on USG and may show posterior shadowing.
These are fat-containing, soft, benign tumors in the breast, with varying amount of fibrous tissue. On USG, they are heterogeneous with hypoechoic and echogenic areas within them.
Ductal carcinoma in situ may or may not be seen on USG. It may appear as a small mass or as an ill-defined hypoechoic lesion, with echogenic foci within due to microcalcifications [Figure 13].
These are usually irregular, ill-defined, or microlobulated, and show posterior shadowing. They may be taller than wide [Figure 14] and show a retraction pattern on 3D coronal imaging [Figure 3]. Microcalcifications may be seen as echogenic foci within the lesion.
This is the second most common breast malignancy and may be seen in elderly women. It is often missed on mammography. On USG, its appearances are variable, ranging from lesions similar to ductal carcinomas to barely visualized areas of architectural distortion with picket-fence shadowing [Figure 15]. Some of these tumors may be occult on USG.
These are uncommon, benign-appearing lesions, which may be homogenous, hypoechoic, and well-circumscribed on USG [Figure 16].
These are also uncommon and benign-appearing. The mucin within may be echogenic on USG and the lesion may show posterior enhancement.
This is a form of ductal carcinoma involving the epidermis, affecting mainly the nipple, areola, and the surrounding region. Mammography and USG may even be normal. MRI may be useful to determine the extent of the disease. Diagnosis is done by skin biopsy [Figure 18].
This is an aggressive form of breast cancer where the cancer is more diffuse, clogging the lymphatic system under the skin. It is often mistaken for mastitis as the symptoms are very similar and because sometimes there is partial resolution after a course of antibiotics. Mammograms show increased density of the affected breast. MRI may be better for diagnosis. USG shows skin thickening, edema [Figure 19], and enlarged lymph nodes. Core biopsy of the lymph nodes or of the skin may help in diagnosis.
Recurrence may occur even years after treatment of the primary breast cancer. It may occur in the residual breast or even in the chest wall following mastectomy [Figure 20].
MRI is more accurate in evaluation of breast implants and implant-related complications. The intact implant has smooth margins and may show some undulations as well as minimal peri-implant fluid [Figure 21A]. An echogenic capsule is seen, forming a triple line surrounding the completely anechoic implant. Rupture may give rise to multiple, linear echogenic lines in the implant – forming a step-ladder pattern [Figure 21B] – and silicone lying outside the implant may give rise to the snow-storm sign of extracapsular rupture. There is no increased incidence of breast cancer in patients with implants [Figure 21C], but it may be difficult to detect in the presence of an implant.
In the male breast, gynecomastia is more common than malignancy. It is seen as an ill-defined hypoechoic swelling behind the nipple, appearing similar to glandular tissue in the female breast [Figure 22].
About 1% of all breast cancers occur in males. USG findings are similar to those of female breast cancer [Figure 23].
Breast cancer can quite often be multifocal [Figure 24], multicentric, or even bilateral. Lobular carcinomas are more notorious for being mulifocal.
USG considerably improves the visualization of tumors in radiodense breasts. It improves the specificity of mammography, and when used to complement mammography, it adds more value to the diagnosis. With a cross-sectional imaging technique, tissue visualization free from overprojection is possible. Contour analysis, exact size, and internal tissue composition of tumors can be evaluated. Lesions located in the breast periphery or close to the chest wall can be studied better.
Source of Support: Nil
Conflict of Interest: None declared.