Microcalcification can be the result due to gestational hyperplasia associated with pregnancy and secretory hyperplasia associated with breast-feeding in mammography. This calcification looks mostly round and focal or diffuse distribution, but rarely shows a irregular, linear distribution, branching pattern. Round and small punctate calcifications represent lobular acinar proliferation and linear distribution represents the growth of the cannulated (Fig. 5) [23-25].

Bloody nipple discharge does not occur commonly in pregnancy or in a period of lactation. However, it can be cause by even small stimuli because the blood flow in breast increases rapidly and the change of epithelial cells gets even worst in 3rd trimester of pregnancy. Slight bloody nipple discharge can be seen from approximately 20% of nipple discharge during pregnancy and 15% of a period of lactation [26]. This phenomenon mostly stops as the lactate feeding begins, but also has a possibility of a severe case that may persist throughout the whole lactation period. Diagnostic cytology tests must be performed for the wounds of nipples by feeding. If the result, physical examination and ultrasound are normal, the follow up test should be recommended in a timely manner.

If it seems to be abnormal in cytology, galactography should be performed especially when the bloody discharge is observed from one duct. However, it is important to help the patient to be relieved because this kind of bloody discharge is a rare symptom of PABC (Figs. 6, 7) [26-28].

Galactocele is a benign lesion, which is mostly detected after a few weeks or months from the time the patient stopped breast feeding, or during lactation or during the 3rd trimester of pregnancy [11,29]. This means it is surrounded by the epithelial cells and myoepithelial cells and contains liquid that is similar to lactate in cystic changed terminal duct and ductules. Most of the galactoceles are found as painless palpable mass which contains protein, fat, lactose in aspiration analysis and are often accompanied by inflammation and necrosis. Therefore, it is considered that the galactocele is formed by the wall fibrosis due to the inflammatory response of extension of lactate ducts. When the contents leak within the breast, chronic inflammation and fat necrosis are observed [30]. Needle aspiration biopsy is helpful for diagnosis and treatment, however, milk-like liquid during lactation and sticky milky contents after lactation, are found in aspiration [29,31]. If it recurrs even after several aspirations, imaging test is needed. Depending on the proportion of fat and protein in breast milk, mammographic findings of galactoceles may vary, which can be seen as follows.

(1) Pseudolipoma: When a higher fat content, seems to be completely radiolucent mass.

(2) Cystic mass with fat-fluid level: Low concentration of fat content rises up and the liquid sinks to the bottom. It is a diagnostic finding that is seen in the mediolateral oblique view of Mammography.

(3) Pseudohamartoma: Galactoceles does not separate lipid from liquid and it is seen radiologic findings which is simliar to hamartoma that contains high viscosity of breast milk [31].

Sonographic findings of galactoceles may also vary depending on the time and site of lesion. In the acute phase, it may appear as an anechoic unilocular simple cyst or a multilocular cyst with thin septation. It is common multilocular cyst that occurs in peripheral region and it is common unilocular or bilocular cyst that occurs in central region. The intensity of hypoechoic echo increases gradually due to the interface between the fat and water components. In this case, Doppler examination performed by the blood vessels in the center to make sure that no particles moving when you press the transducer lesions may be helpful in the diagnosis. In ultrasound, galactoceles only breast milk composition consists of benign solid masses as shown boundaries if and posterior acoustic enhancement seems clear. A long time later, several ingredients are mixed and if you look inside looks mixed echogenic heterogeneous mass (Figs. 8-10) [11,32-34]. Galactoceles is rich in nutrients, and sometimes it can be infected. This finding is well observed in the ultrasound. Aspiration here, you can see that the purulent fluid and breast milk ingredients are mixed in (Fig. 11). Most natural decay takes over several weeks, but occasionally a more long-lasting.

It's not common to see infections during pregnancy, but it is often observed in lactation. Staphylococcus aureus and Streptococcus, which are common pathogens present in the nose and throat of newborn babies, may infect the breast via the damaged epithelial cells of the nipple-areola complex during breast feeding. Nipple cracks or abrasions of the skin can be often discovered on the patient's past history. If breast milk is stagnant, it would be a good culture medium and cause symptoms [24,29,30]. S. aureus infections, being topical, result in severe clinical symptoms right from the beginning, whereas infections caused by streptococci are diffuse and cause local abscess only in the advanced stage of infection (Figs. 12,13). It is treated well by antibiotics, especially amoxicillin-clavulanate. It is quite rare, but puerperal mastitis by methicillin-resistant S. aureus can be very fatal [35-37]. Mammography should not be performed, unless there are suspicious malignant findings. The reason is that it mostly shows thickening of the skin and fibrous tissue even though it is very severe mastitis. Moreover, it is rare to discover other severe abnormalities. If there is abscess formation suspected, the ultrasound examination is first required for the diagnosis and treatment. Irregular boudaries, hypoechoic or anechoic mass, thick, irregular walls, posterior acoustic enhancement, and liquid debris (fluid-debris) shades can be observed in the abscess. Sometimes the air in abscess can cause bright reflection. These hyperechoic dots floating point is the differentiation of malignant. Mastitis in lactation abscess developed in the subacute form, periarthritis [38,39]. Abscess is easily treated by incision drainage. If the abscess lesion size is less than 3 cm, it can be treated with 14 to 21 gauge needle aspiration. If the abscess lesion size is 3 cm or more, it can be aspirated with the 6 to 8 Fr catheter drainage or surgical drainage. Before doing this, it is important to dry up the abscess first. It is necessary that examiner should irrigate the cavity with normal saline under local anesthesia after the drainage to prevent recurrence [38-40]. After treatment, continuing breast feeding helps improve inflammation and promote drainage. Also, breast feeding can be safely performed during antibiotics therapy [29,35]. If there is no improvement despite these treatments, examiner should suspect tumor and perform cytology test and biopsy.

Granulomatous mastitis occurs mainly in young women, and it is an uncommon type which mainly occurs within five years after pregnancy [41-43]. It exhibits specific histological findings characterized by non-caseating (noncaseating), non-vascular (nonvasculitic) granulomatous inflammatory changes, which can be noted in the center of the lobules. Mammographic findings are diverse from normal to benign with focally asymmetric shadow and malignant. Sonographic findings helpful in diagnosis are multiple appearances, which often show hypoechoic and sometimes large hypoechoic mass in adjacent lactiferous gland (Fig. 14) [43]. However, it requires special attention in diagnosis because it is not well differentiated from malignancy, and reactive lymphadenopathy is observed in about 15%. Local excision can be a treatment [40-46], but sometimes it disappears naturally. Therefore close follow-up is necessary [47].

Benign proliferative lesion is a common type because of the influence of hormones during pregnancy and lactation. Juvenile papillomatosis of the breast rarely occurs in young women, and it is characterized by ductal hyperplasia and papillary proliferation of the wall surrounding its sac [48]. It is seen as a hypoechoic mass with an unclear margin in an ultrasonogram, and no specific findings, except an asymmetric shadow, is seen in a mammogram; however, sometimes microcalcification can be observed. The treatment is a surgical resection. It is important to check if the resection margin is completely negative when it comes to preventing recurrence.

Lactating adenoma is a benign tumor mainly caused by the physiological changes that occur during pregnancy and lactation. This typically occurs during feeding or the third trimester of pregnancy. Lactating adenoma is sometimes interpreted as a variant of fibroadenoma, tubular adenoma, or lobular hyperplasia, which are also caused by physiological changes [49-51]. Fibroadenoma is mixed with stromal and epithelial components. Lactating adenomas, however, only consists of epithelial component. Grossly, it seems to be a certain boundary and elastic mass. Histologically, it is densely packed with lobules, which are separated from each other by a thin connective tissue. Lactating adenoma is composed of acinars and mature thin tubes and filled with secretion is softer than a fibroadenoma The physiological changes that occurs in the surrounding normal parenchyma takes place in the lesions of the internal secretion and secretory hyperplasia appears [49-51]. Lactating adenoma can naturally disappear at the end of pregnancy or lactation. It may also disappear by necrosis, like a fibroadenoma [52]. Most of Lactating adenoma does not relapse after complete resection. Lactating adenoma accompanying malignant lesions is very rare. And it does not increase the risk of breast cancer. It is difficult to distinguish between a lactating adenoma and a fibroadenoma by imaging. A radiolucent or hyperechoic area, which indicates fat content of breast milk, according to lactation hyperplasia, can be seen on mammography or ultrasonography and is useful in diagnosis (Fig. 15). It appears to be a small hypoechoic mass, which is difficult to distinguish from the surrounding tissue on ultrasonography. Moreover, because of its posterior acoustic enhancement and hormonal changes, it appears hypervascular in color or output Doppler. Occasionally, the differential diagnosis of malignant lesions is difficult mainly due to unclear boundaries, microlobulated periphery, reducing posterior acoustic effect, structural heterogeneity. And it occurred by the necrosis of lactating adenoma [11,53-55].

PABC is defined as breast cancer that occurred during pregnancy and after delivery within one year, represents up to approximately 3% of all breast cancers, occurring in one incidence per 3,000 to 10,000 pregnancy. Delay of childbirth age shows increased prevalence and advanced stage at the time of diagnosis and poor prognosis and seems that more than 50% are high-grade tumors [29,62,63]. And large number of them are form of inflammatory tumor and shows in more than 50% lymph node metastasis, negative at hormone receptor and positive at HER2/neu [62,63]. Late diagnosis of tumors owing to the biological effects of pregnancy results in poor prognosis and rapid tumor growth; recurrence is common within 2 to 3 years of the diagnosis [29,62,63].

Mostly palpable lesions and clinical symptoms are visible swelling, redness, and diffuse mastosis at locally advanced carcinoma [29,62,63]. The imaging findings of breast cancer in non-pregnant women are not significantly different from those in pregnant women due to the increase in glandular density. Even in non-pregnant women, mammography has low sensitivity, and ultrasound is considered a better diagnostic tool [7-12].

The mammary gland undergoes clinical and physiological changes during pregnancy, making imaging diagnosis difficult. The majority of patients with advanced stage looks so delayed diagnosis is as follows [64,65].

During pregnancy is known to be delayed an average of 5 to 7 months of breast cancer diagnosis, whenever be delayed one month diagnosis shows increased by approximately 0.9% to 1.8% of axillary lymph node metastasis [66].

In most cases, it appears as a breast mass with no associated pain, and sometimes, it can be found on breast examination in the absence of breast feeding [66]. During the third trimester of pregnancy, hemoid secretion is often seen due to loss of epithelial cells alike papilloma in lactiferous drifts and this is a common symptom.

Cytological examination will be carried out when hemoid secretion is continued more than 2 months after delivering.

Although mammography is not effective in pregnancy because physiological changes decreased sensitivity and specificity, it is performed suspected malignancy. 68% to 74% of PABC has abnormal findings with mammography and 90% of PABC has Breast Imaging Reporting and Data System (BIRADS) 3 to 4 score. During pregnancy, ultrasound seems the most effective imaging studies in the diagnosis of breast disease. And it's sensitivity to the breast disease is 93% to 98% (Figs. 17, 18). Complex echo pattern, posterior acoustic enhancement is a common finding in the PABC compared with non-pregnancy breast cancer. Necrosis or cystic change is seen in the carcinoma present non-echo pattern and posterior acoustic enhancement because tumor grows up quickly by stimulation of the hormonal changes in pregnancy.

Carriers with breast cancer (BRCA)1 or BRCA2 mutation are at high risk for breast cancer. Therefore carriers with BRCA1 or BRCA2 mutation certainly needs to undergo strict clinical and image examination before and after pregnancy. This strict examination uses ultrasonography and MRI, but ultrasonography is more useful than MRI because the latter is difficult to find during the period of lactation (Fig. 19).

According to former studies, the PABC prevalence of carrier with BRCA1 mutation is higher than BRCA2 mutation [67]. Carriers of mutations in the BRCA1 or BRCA2 genes who have parity have an increased risk of PABC than those who do not have parity before the age of 40 years, and pregnancy at an early age does not decrease the prevalence [68]. But it was recently reported by International BRCA1/2 Carrier Cohort Study (IBCCS) that carriers with BRCA1, BRCA2 malignant and control group has decreased the risk of being malignant after the age of 40 years [69].