Key words breast - guideline - gynecology - DEGUM - ultrasound
1. Introduction
Breast cancer is the most common malignant disease in women in western industrialized
countries. According to current data of the Robert Koch Institute, 67 300 women were
diagnosed with breast cancer in 2017 in Germany[1 ]. On the base of current data 1 of 8 women develops breast cancer once in her lifetime.
There are multiple methods for detecting breast cancer early. Mammography screening
is available to all women between the ages of 50 and 70 in Germany. However almost
3 from 10 women diagnosed with breast cancer are younger than 55 and 30 % are older
than 70. Breast ultrasound has a very important status in the assessment of breast
findings.
The goal of this Best Practice Guideline is to meet quality assurance requirements
and to ensure that breast ultrasound is performed in a standardized manner. The guidelines
are based on the standards recommended and practiced by the Breast Ultrasound Working
Group of the DEGUM.
2. Fundamentals of breast ultrasound
2. Fundamentals of breast ultrasound
Ultrasound is an imaging method for diagnosing diseases of the breast that is characterized
by minimal stress for the patient, a lack of radiation, low cost, and ubiquitous availability.
It is used to clarify clinically and radiologically conspicuous findings and to monitor
biopsies and interventions. It is an established part of aftercare and is a supplementary
method for the early detection of breast cancer in dense breast tissue and in young
women and in the case of a high risk of breast cancer.
High breast density presents a diagnostic challenge in the case of mammography [5 ]. Although there is no linear relationship between breast density and breast cancer,
the diagnostic reliability of radiology decreases with increasing breast density [6 ]. The denser the tissue the more difficult it is to assess and detect a malignancy
[7 ] and the greater the risk of malignancy [8 ]. According to the current S3 guidelines, supplementary breast ultrasound is indicated
in the case of dense breast tissue [9 ]. According to data from the Mammography Screening Program, 46 % of women over the
age of 50 have dense breast tissue and approx. 6 % of women have extremely dense breast
tissue [10 ]. Dense breast tissue presents less of a diagnostic challenge for breast ultrasound
than mammography [11 ]. The use of breast ultrasound in addition to mammography increases the detection
rate for breast cancer [11 ]
[12 ]
[13 ].
To ensure examination quality, it is important to comply with technical requirements
and particularly examiner qualifications. Main factors influencing the quality of
the diagnostic results of an ultrasound examination include the quality of the equipment
being used and the frequency of the transducer.
3. Examination technique
Patient positioning
The patient should ideally be in a supine position. The ipsilateral arm should be
elevated at least 90 degrees and the corresponding hand should be placed behind the
head. This allows a comfortable and seamless examination of the breast, axilla, and
the supraclavicular and infraclavicular lymph nodes. Lifting the arms, unilaterally
or bilaterally, also causes the pectoral muscles to tense thereby causing the breast
to flatten and stay in place. The latter is only applicable on a limited basis for
patient with macromastia. Due to increased mobility of the breast in such cases, the
supine position should be adapted during the examination by lifting the ipsilateral
shoulder region so that the breast is medialized as a result of the rotation of the
body. The examination can then be performed with fewer problems and in its entirety.
Examination procedure and handling of the transducer
It is helpful to hold the transducer at the base, while “resting” the hand holding
the transducer on the breast. Holding the transducer without support should be avoided.
Application pressure should be selected so that the anatomy is visualized on the B-mode
image without artifacts and the amount of pressure applied to the breast is not uncomfortable
for the patient. Including orientation points like the clavicle, sternum, ribs, and
nipple-areola complex allows continuous image interpretation without the examiner
having to change the field of view intermittently.
The goal is the complete examination and documentation of both breasts, the axillae,
and the supraclavicular and infraclavicular lymphatic drainage regions where appropriate.
In practice, four main transducer and scan orientations are used in breast ultrasound.
The examiner decides which technique to use. However, it is important that the entire
breast is scanned and visualized in an overlapping manner. The four basic techniques
are:
Sagittal/parasagittal scan orientation: The transducer is applied perpendicular to the breast region. This results in a sagittal
or parasagittal slice plane. The breast is examined fully from the anterior axillary
line to the parasternal line in a meandering pattern by moving the transducer horizontally
([Fig. 1 ]). To examine the entire breast, the transducer is always moved caudally or cranially
less than the width of the transducer.
Transverse/horizontal scan orientation: The transducer is applied horizontally so that a transverse view on the B-mode image
is achieved. Examination of the breast is also performed in a meandering pattern,
from cranial to caudal. The transducer is again moved medially or laterally by slightly
less than the width of the transducer ([Fig. 2 ]).Fig. 1 ], [2 ]).
Antiradial/tangential scan orientation: This approach is particularly suitable for evaluating larger breasts but can also
be used as an alternative to the aforementioned methods. The transducer is applied
tangentially to the base of the breast and is moved from the periphery toward the
center perpendicular to the lactiferous ducts in clockwise direction toward the nipple.
It must be ensured that there are complete regions of overlap particularly in the
periphery ([Fig. 3 ]).
Radial scan orientation : A radial scan orientation is suitable particularly for tracking ductal structures.
This approach is thus primarily used to diagnose duct ectasia and intraductal formations
([Fig. 4 ]). The transducer is moved from the periphery in a central direction along a lactiferous
duct and then in a clockwise direction to the next lactiferous duct, which is then
followed from the periphery in a central direction to the nipple.
Fig. 1 Sagittal/parasagittal scan orientation.
Fig. 2 Transverse/horizontal scan orientation.
Fig. 3 Antiradial/tangential scan orientation.
Fig. 4 Radial scan orientation.
Regardless of the selected technique, the examination must be performed in an overlapping
manner without any gaps so that even small pathological findings are not missed.
Sonopalpation and compression
In the age of shear wave elastography and strain elastography, sonopalpation with
manual compression for the evaluation of the elasticity of findings visible on ultrasound
is considered secondary but is a good tool for optimized visualization.
4. Sonoanatomy of the breast and axilla
4. Sonoanatomy of the breast and axilla
Ultrasound evaluation of the breast and axilla requires exact knowledge of the physiological
and anatomical conditions.
Sonoanatomy of the breast
The visible part of the mammary gland is located on the chest wall between the second
and the seventh rib, with the subcutaneous body of the mammary gland overlying the
fascia of the pectoralis major muscle. The body of the mammary gland is comprised
of approximately 15–20 individual lobes that are situated radially around the nipple.
The individual excretory ducts open to one or multiple lactiferous ducts in the nipple.
The lobes are surrounded by connective tissue and the Cooper ligaments that stretch
subcutaneous to prepectoral and provide support to the breast. A layer of fat tissue
separates the body of the mammary gland from the skin as well as from the pectoralis
muscle fascia.
To systematically scan the individual anatomical breast structures, the transducer
should be moved in a meandering pattern transverse or sagittal or antiradial (see
chapter 3).
In the cross section of the breast ([Fig. 5 ], [6 ]), the sonomorphologically relevant structures can be followed from anterior to posterior
([Fig. 7 ]) [14 ]:
Fig. 5 Schematic cross section of a breast © LOGO! Design & mehr.
Fig. 6 Ultrasound image correlating to [Fig. 5 ].
Fig. 7 B-mode image with sonomorphologically relevant structures: a hyperechoic skin, b hypoechoic fat tissue, c hyperechoic fibroglandular tissue, d hyperechoic Cooper ligament, e pectoralis major muscle.
Hyperechoic skin and hypoechoic nipple,
Hypoechoic subcutaneous fat tissue and hyperechoic Cooper ligaments
Hyperechoic fibroglandular tissue
Hypoechoic retromammary prepectoral fat tissue
Hyperechoic fascia of the pectoralis major muscle.
Thoracic wall with musculature and ribs
It must be taken into consideration that the fine structure of the mammary gland and
thus also the sonomorphological image can be affected by hormonal status among other
things [15 ]
[16 ]. In premenopausal women, breast tissue is affected by estrogen and progesterone
with the lobes temporarily enlarging and the connective tissue retaining fluid after
ovulation in the middle of the cycle. The typical sonomorphological image of the breast
in a young premenopausal woman usually shows mostly dense fibroglandular tissue and
just a few fat lobules ([Fig. 8a ]). The amount of functioning glandular tissue decreases with age while the amount
of fat increases. With the start of menopause and the associated decrease in estrogen,
the fibroglandular tissue atrophies and fat tissue becomes dominant (involution) ([Fig. 8b ]) [3 ].
Fig. 8 a Premenopausal. b Postmenopausal.
Pregnancy and lactation result in physiological and thus sonomorphological changes
in the breast. The constant estrogen and progesterone levels from the placenta and
the prolactin from the pituitary gland during pregnancy result in ductal-lobular proliferation.
The mammary gland cells differentiate to milk-producing alveolar cells within the
lobes (lactogenesis). This proliferation and differentiation can be correlated sonomorphologically
with an increase in volume and density of the gland ([Fig. 9a ]). In addition, there is increased perfusion of the gland ([Fig. 9b ]) and enlargement of the lactiferous ducts due to lactogenesis ([Fig. 9c ]).
Fig. 9 Sonomorphological changes during pregnancy and lactation: a Increased density of the glandular tissue, b Increased perfusion, c Enlargement of the lactiferous ducts.
Sonomorphologically, the male breast is mainly comprised of hypoechoic fat tissue
interspersed with hyperechoic reticular connective tissue ([Fig. 10a ]). However, in the event of a hormonal imbalance with a lack of male hormones and
an excess of estrogen (e. g., due to chronic disease or medication), gynecomastia
can occur [17 ]. Histology shows fibrosis of the parenchyma associated with epithelial hyperplasia
of the glandular ducts, sonomorphologically recognizable as predominantly retroareolar
hypoechoic fibroglandular tissue ([Fig. 10b ]).
Fig. 10 a Retroareolar visualization of normal male breast. b Gynecomastia, retroareolar hypoechoic glandular tissue.
Sonoanatomy of the lymphatic drainage regions
Axillary ultrasound is indicated for early detection, preoperative sonographic lymph
node staging, and aftercare [18 ]. Precise anatomical knowledge of the guide structures is a requirement for correct
topographical classification and visualization of the individual lymph node region
levels I-III ([Fig. 11 ]). Level I is bordered laterally by the humeral head and the latissimus dorsi muscle,
cranially by the axillary artery and vein, and medially by the pectoralis minor muscle.
Level II stretches from the lateral to the medial margin of the minor pectoralis muscle.
Abnormal lymph nodes are located in the underlying fat tissue or between the pectoralis
major and the pectoralis minor muscles (interpectoral (Rotter) group). Level III is
defined as the region medial to the pectoralis minor muscle.
Fig. 11 Sonographic visualization of lymph node regions: Level I (green), level II (red),
level III (blue).
The following criteria are used for the sonomorphological assessment of nodal status:
Lymph node shape, corticomedullary ratio, structure, and vascularization [18 ]
[19 ], with a multimodal approach being used. A histologically benign lymph node appears
oval in shape, with a hyperechoic fatty central hilar area, histomorphologically corresponding
to the medulla, and a thin hypoechoic rim, corresponding to the cortex ([Fig. 12 ]) [18 ]. Isolated blood vessels are seen in a central location. An increase in the central
hyperechoic core usually associated with an increase in the size of the individual
lymph node is caused by reactive-inflammatory processes occurring over the course
of a lifetime. These lymph nodes with a central massive collection of hilar fat are
also to be assessed as benign.
Fig. 12 Benign oval lymph node with: a hypoechoic cortex and b hyperechoic medulla.
Metastases follow the lymphatic drainage usually from the periphery (cortex) toward
the center (medulla) with the corticomedullary structure changing sonomorphologically
as follows ([Fig. 13a–d ]) [18 ]
[19 ]:
Fig. 13 a Malignant lymph nodes with asymmetrical enlargement of the hypoechoic cortex. b Malignant lymph node with loss of the corticomedullary structure. c Malignant lymph node with subcapsular vascularization. d Malignant lymph node with extracapsular invasion of the surrounding tissue.
Asymmetric enlargement of the hypoechoic peripheral zone (cortex) and thus compression
of the hyperechoic medullary structure
Loss of the corticomedullary structure due to loss of the hyperechoic medullary structure
and transition to a hypoechoic round structure
Subcapsular, peripheral, aberrant vascularization
Extracapsular invasion of the surrounding tissue and irregular outer contour
Hypoechoic areas are the result of localized malignant infiltration. However, they
can also be observed in the case of pronounced inflammatory liquefaction with focal
coagulation necrosis in systemic lymphadenopathies, for example. The supplementary
use of US elastography with the identification of “hard” lymph node areas can be used
for further differentiation between benign and malignant lymph nodes [20 ]. Metastases change the corticomedullary structure and thus the sonomorphological
relationship between the longitudinal and transverse diameter of the lymph node. The
Solbiati index describes the ratio of the longitudinal diameter to the transverse
diameter and can be used as a further criterion for assessing malignancy. Therefore,
a Solbiati Index of < 1.5 indicates malignancy, while an index value of > 2 tends
to indicate benign lymph nodes [21 ].
Due to the improved spatial and contrast resolution of modern high-frequency ultrasound,
a cortical thickness of ≤ 3.0 mm is considered a significant and accurate criterion
of a lymph node not requiring clarification according to current data. The likelihood
of metastases increases with the thickness of the cortex [22 ].
A further rare but specific sign of lymph node metastasis is an irregular nodular
outer contour due to extracapsular invasion of the surrounding tissue ([Fig. 13 d ]) [23 ]. Semiquantitative evaluation of the total vascularization also contributes to the
differentiation between benign and malignant lymph nodes. Therefore, benign lymph
nodes show only isolated hilar blood vessels, while malignant lymph nodes can show
peripheral cortical vascularity as well as aberrant vessels or locally absent vascularity
([Fig. 13c ]).
5. US-DEGUM categories, assessment criteria, and documentation
5. US-DEGUM categories, assessment criteria, and documentation
5.1 US-DEGUM categories
In general, the final evaluation of a breast ultrasound examination includes assessment
of the parenchyma (parenchyma category) and one or more potential findings (assessment
category).
Assessment categories
In addition to an insufficient ability to evaluate a lesion (US category 0) and already
histologically confirmed malignant findings (US category 6), there are five more assessment
categories:
0 Diagnostic imaging insufficient, additional diagnostics required
1 Inconspicuous with no lesions, tiny simple cysts and retroareolar, symmetrical ductectasia
are not described separately
2 Benign findings, e. g., uncomplicated larger cysts, known fibroadenomas, intramammary
lymph nodes, fat necrosis, implants, scars that remain constant over time, and scars
that decrease in size
3 Probably benign findings requiring monitoring (risk of malignancy ≤ 2 %)
4 Suspicious for malignancy (risk of malignancy > 2 % to < 95 %) – histological examination
required anstatt necessary
5 Highly suspicious for malignancy (risk of malignancy ≥ 95 %) – histological examination
required
6 Histopathologically confirmed malignancy
A category is assigned to every breast after description of all findings. The finding
with the highest (worst) category is always the assessed category.
Parenchyma categories
Breast density can still be determined on a percentage basis of fibroglandular tissue
(I–IV) analogous to mammography assessment in the fourth edition of the ACR Breast
Imaging Atlas from 2003 [4 ], the DEGUM recommendations from 2006 [3 ], and the WOBI recommendations from 2016 [24 ]. However, objective determination is significantly more difficult in this form on
ultrasound than on mammography. Only volumetric measurement of the entire breast in
the form of automatic three-dimensional breast ultrasound (ABUS) allows objective
computer-based determination of the percentage of fibroglandular tissue.
A critical discussion regarding the ability to evaluate the parenchyma was also held
in 2016 by 11 professional societies including the DEGUM [25 ].
Therefore, analogous to the current mammography and MRI assessment in the 5th edition of the ACR Atlas [26 ]
[27 ], the DEGUM recommends using 4 categories to describe tissue composition ([Fig. 14 ], [15 ], [16 ], [17 ]):
Fig. 14 Parenchyma category a, almost entirely fatty tissue, easy to assess.
Fig. 15 Parenchyma category b, balanced admixture off fat and fibroglandular tissue, easy
to assess.
Fig. 16 Parenchyma category c, almost entirely fibroglandular tissue, easy to assess.
Fig. 17 a Parenchyma category d, extreme fibroglandular tissue, without compression, difficult
to assess. b Parenchyma category d, extreme fibroglandular tissue, same finding as in Fig. 18a
but with compression.
a Almost entirely fatty tissue ([Fig. 14 ])
b Balanced admixture of fat and fibroglandular tissue ([Fig. 15 ])
c Almost entirely fibroglandular tissue ([Fig. 16 ])
d Extreme fibroglandular tissue ([Fig. 17a, b ])
with the addition of “easy to assess” or “difficult to assess”
It should be mentioned if the breast tissue is homogeneous and assessable in its entirety
and than “easy to assess” or if the breast tissue is inhomogeneous and/or not assessable
in its entirety and so “difficult to assess”.
Example 1
Involution in the case of gigantomastia can be evaluated as “almost entirely fatty
tissue, difficult to assess” due to the size of the breast. If no lesion can be detected,
the final assessment would be: “Parenchyma category a, difficult to assess, assessment
catgory 1” or shortened form: DEGUM category a/1, difficult to assess .
In the case of fibroglandular tissue, the examination must be optimized by the selection
of the ultrasound modes, the examination technique, the US system, and the transducer
technology to ensure the ability to assess. The basic factors here are compression,
frequency, focus setting, and time gain compensation to minimize artifacts and limitations
and to optimize assessment.
The percentage of fibroglandular tissue plays a subordinate role in assessment a–d.
For the final categorization not only the ratio of fat tissue to glandular tissue
but also primarily its structure is essential. Extreme fibroglandular tissue is present
when there is alternation between pronounced hyperechoic and hypoechoic areas and
acoustic shadowing artificially increases the heterogeneity of the tissue and the
sensitivity of sonography can be affected, particularly in deeper layers. In spite
of the mentioned optimization of the ultrasound system, assessment is only possible
on a limited basis.
Example 2
In the case of a small breast that can be evaluated in its entirety up to the muscle
fascia, the ability to assess is to be categorized as “easy to assess” in spite of
extreme fibroglandular tissue. If no lesion is detected, the final assessment would
be: “Parenchyma category d, easy to assess, assessment category 1” or in shortened
form: DEGUM category d/1, easy to assess .
5.2. Indications for breast ultrasound
Clarification of unclear clinical findings (palpation findings, inflammatory changes,
conspicuous cutaneous findings, nipple discharge) [9 ]
Clarification of mammographic and MRI findings in categories 0, 3, 4, and 5 [9 ]
[25 ].
Differentiation between cystic and solid lesions
In addition to mammography in the case of dense breast tissue
First imaging choice in women < 40 years
First imaging choice in pregnancy and lactation
Increased risk of breast cancer
Follow-up in the case of neoadjuvant chemotherapy
Ultrasound guidance for puncture procedures, biopsies, and marking [28 ]
[29 ].
Intraoperative tumor detection and target control [30 ]
[31 ]
Specimen ultrasound [32 ]
Evaluation of lymph nodes
In aftercare in addition to mammography including locoregional lymphatic drainage
regions
Evaluation of implants and their anatomical location [33 ]
5.3. Ultrasound DEGUM assessment criteria
Focal lesions ([Fig. 18 ])
Fig. 18 Diagram of the most important assessment criteria for focal lesions with allocation
to probably benign and probably malignant findings (based on Madjar et al. [3 ]).
Calcifications:
Suspicion of calcifications must always be correlated with a current mammography examination
Associated features:
Architectural distortion
Ductal changes
Skin changes
Edema
Vascularity – absent, internal vascularity, vascularity in rim
Elasticity – soft, intermediate, hard
Special cases:
Simple cysts
Clustered microcysts
Complicated cysts
Lesions in/on the skin
Foreign body, including implants
Intramammary lymph nodes
Locoregional lymph nodes
Postsurgical fluid collection – seroma, hematoma
Fat necrosis
5.4. Equipment/image settings
Use the entire field of view, the thoracic wall is visible on the lower edge of the
image (min. 2/3 of the image should contain mammary gland tissue) ([Fig. 19 ])
Correct focus setting depending on the location of the lesion (caution: too many foci
slow image reconstruction) ([Fig. 19 ])
Larger lesions should also be fully visualized if possible – use panorama images or
combined separate images
Adapt the time gain compensation
Select the highest possible acoustic frequency
Optimize the brightness of the image on the monitor and printer
Compare and use compound imaging, harmonic imaging, and non-contrast-enhanced B-mode
imaging for better assessment of the margins of the lesion and the posterior acoustic
features [36 ]
Fig. 19 Correct image setting with use of the entire field of view, correct focus setting
at the level of the lesion with the lesion in the center of the image.
5.5. Image documentation
Name of the facility
Examination date
Patient name/date of birth and/or ID
Pictogram with correct display of the transducer orientation
Objectively reproducible measurements of the lesion on two perpendicular planes with
specification of three diameters starting from the plane with the greatest diameter
and determination of the tumor volume if applicable ([Fig. 20 ], [21 ]).
Inclusion of the hyperechoic rim if present.
Standardized measurements with the transducer perpendicular to the skin, particularly
important for follow-up during neoadjuvant chemotherapy.
Skin distance from the tumor: Upper edge of the tumor to the lower edge of the cutis
as on-to-on measurement (independent measurement of postoperative, radiogenic, or
inflammatory changes of the cutis)
In the case of multiple lesions, separate documentation with schematic drawing of
location
If the ultrasound examination is inconspicuous, the minimum documentation (2 images)
consists of one image of the upper-outer quadrant on the right and one image of the
upper-outer quadrant on the left. Additional image documentation of a representative
lymph node of both axillae is recommended.
In the case of an abnormal ultrasound examination, all conspicuous findings regarding
the mammary gland and the locoregional lymphatic drainage regions should be documented
in writing and images. The supraclavicular fossa should also be examined in the case
of abnormalities on level II and/or III.
Fig. 20 Measurement of two perpendicular diameters in the plane with the greatest lesion
diameter. Correct use of the entire field-of-view. Correct display of the transducer
in the pictogram.
Fig. 21 Measurement of the third diameter (same lesion as in [Fig. 20 ]) on the plane perpendicular to the first plane and calculation of the tumor volume.
Measurement of the distance to the skin (on-to-on). Exact specification of the location.
Correct display of the transducer in the pictogram.
5.6. Documentation of ultrasound findings
Name of the facility, name of the examiner, date of the examination
Patient data: Name, date of birth, ID if applicable
Issue/indication
Medical history
Inspection and palpation
Assignment of breast ultrasound findings to DEGUM categories
Description of the lymph nodes
Description of the parenchyma and the ability to assess according to parenchyma categories
a-d with the addition of “easy or difficult to assess” (see 5.1).
Description of suspicious lesions according to the DEGUM assessment criteria (see
5.3)
Lesion location data – clockwise orientation, distance from the skin, distance from
the nipple (not the areola since it differs in size based on anatomy and can change
after pregnancy or surgery)
US assessment categories 0–6 (see 5.1)
Correlation of findings to symptoms and any preceding ultrasound examinations or other
examinations like mammography or MRI
Recommended procedures
