Breast cancer ultrasound: what it shows, what the tumor looks like, and what BI-RADS means

Breast ultrasound is one of the primary diagnostic methods for suspected breast cancer and an important adjunct once a diagnosis has been established. Ultrasound helps visualize nodular or non-nodular lesions, assess their shape, edges, orientation, and internal structure, examine axillary lymph nodes, and perform a targeted biopsy. However, ultrasound alone cannot definitively confirm cancer—the diagnosis is made through tissue examination. [1]

Breast cancer often appears on ultrasound as a hypoechoic, irregularly shaped mass with fuzzy, angular, or spiculated margins and sometimes a non-parallel orientation—a so-called "taller than wider" growth pattern. However, none of these features is absolute: some malignant tumors may appear relatively round and well-circumscribed, and benign lesions sometimes have suspicious features. [2]

The most important part of the report is the resulting BI-RADS category. BI-RADS 1-2 typically means no suspicious finding or benign changes; BI-RADS 3 is a likely benign lesion that usually requires observation; BI-RADS 4-5 means that a biopsy should be considered; BI-RADS 6 is used when malignancy has already been confirmed by biopsy. The updated BI-RADS v2025 system will be in effect from the end of 2025. [3] [4]

A normal ultrasound also does not provide an absolute guarantee of the absence of cancer. Ultrasound is particularly poor at detecting certain calcifications, ductal carcinoma in situ, and individual infiltrative tumors. If a mass remains clinically suspicious, normal images should not automatically terminate the examination. [5]

Why is an ultrasound performed if breast cancer is suspected?

The primary goal of an ultrasound is to understand the specific features of a detected lump or other findings and determine whether a biopsy is necessary. Ultrasound is particularly well suited for targeted assessment of a specific area of the breast and allows for examination directly at the point felt by the patient or physician during palpation. [6]

Ultrasound can differentiate a simple fluid-filled cyst from a solid mass, examine the structure of a solid nodule, and determine its precise dimensions in several planes. The radiologist also evaluates surrounding tissue, skin, ducts, and regional lymph nodes, if necessary. [7]

Age and clinical situation significantly influence the sequence of examinations. In women under 30 years of age with a new palpable mass, ultrasound is usually the first imaging method. In women 40 years and older, the initial examination often includes diagnostic mammography or digital tomosynthesis, with ultrasound used as an additional targeted method. For women aged 30-39 years, both ultrasound and diagnostic mammography/tomosynthesis are acceptable, depending on the circumstances. [8]

If mammography in a woman over 40 years of age does not reveal an explanation for a palpable lump, targeted ultrasound is usually considered an appropriate next test. It can detect some lesions that are difficult to see on mammography. [9]

In patients with confirmed invasive cancer, ultrasound is used for more than just re-examination of the tumor itself. The ACR considers breast ultrasound a generally appropriate test for the initial assessment of the locoregional spread of early invasive cancer. [10]

The main tasks of ultrasound

Clinical situation	What does an ultrasound help with?
A seal was detected	Find its visual equivalent and characterize it
A mass was detected on mammography.	Determine whether it is solid or cystic and evaluate the morphology
Mammography is negative, but the lump remains.	Search for a mammographically occult formation
A suspicious node is visible on ultrasound	Perform a biopsy under ultrasound guidance
Cancer has already been confirmed	To clarify the sizes and locoregional findings
Suspected axillary node involvement	Assess their structure and select a node for biopsy
Neoadjuvant treatment	Monitor changes in tumor size in combination with other methods

[11]

What does breast cancer look like on ultrasound?

The classic suspicious ultrasound image is a solid, hypoechoic, irregularly shaped mass with fuzzy or spiculated edges. However, cancer has many variations in appearance, so a diagnosis cannot be made based on a single feature. [12]

The term "hypoechoic" means that the area reflects ultrasound waves less strongly than the surrounding tissue and therefore appears darker on the screen. This is a very common sign of cancer, but it is nonspecific: many fibroadenomas and other benign lesions are also hypoechoic. [13]

Shape is important. Irregular shapes are more common in malignant tumors than oval shapes. Spiculated margins—thin bands extending from the tumor into the surrounding tissue—are particularly suspicious. However, even this feature is not sufficient for a definitive diagnosis without a biopsy. [14]

Another important parameter is orientation. A benign tumor often grows parallel to the skin and appears wider than tall. A malignant tumor may cross normal tissue planes and have a non-parallel orientation—colloquially, this is sometimes referred to as "taller-than-wide." [15]

An acoustic shadow sometimes appears behind a tumor: the ultrasound signal weakens, and the deeper tissue appears dark. This may be due to a dense fibrous reaction around the tumor, but posterior acoustic shadowing also occurs in some benign processes. [16]

The radiologist evaluates not only the nodule itself. Architectural deformation of surrounding tissues, swelling, skin changes, and abnormal lymph nodes can also increase suspicion of malignancy. [17]

The most important ultrasound signs

Sign	How is it usually interpreted?
Incorrect shape	Increases suspicion
Speculated edge	One of the most suspicious signs
Angular or fuzzy edge	May be a sign of infestation
Non-parallel orientation	Increases the likelihood of malignancy
Hypoechogenicity	Common in cancer but nonspecific
Rear acoustic shadow	Suspicious in the appropriate context
Architectural deformation	Requires careful assessment
Skin changes/swelling	May accompany a common process
Abnormal lymph nodes	May indicate regional spread

[18]

Can cancer look benign on ultrasound?

Yes. A relatively smooth shape or clear edges do not guarantee benignity. This is one of the reasons why a radiologist evaluates a combination of features, clinical history, and other imaging findings rather than relying on a single image. [19]

A good example is triple-negative breast cancer. A systematic review showed that such tumors do not always exhibit the typical set of "malignant" ultrasound characteristics. Therefore, a single, supposedly reassuring feature cannot reliably exclude this biological subtype. [20]

Invasive lobular carcinoma can also pose diagnostic challenges. It often grows infiltratively without a compact nodule, so it may manifest as only an acoustic shadow or subtle architectural deformity and sometimes remains barely visible on ultrasound. [21]

This is why the concept of non-mass lesion—a non-nodular finding—has been further developed in BI-RADS v2025 for ultrasound. The current system recognizes that a pathological process does not necessarily form a classic round or irregular "node." [22]

What does BI-RADS mean on a breast ultrasound?

BI-RADS is not a diagnosis, but a standardized category indicating the level of radiological suspicion and recommending the next step. The system is used for mammography, ultrasound, and magnetic resonance imaging. [23]

In December 2025, the American College of Radiology released BI-RADS v2025, the first major update to the system since the fifth edition. The ultrasound component included updated descriptive criteria, including those for non-nodal findings, elasticity, and more structured lymph node assessment. [24]
[25]

BI-RADS 1 indicates a negative study, BI-RADS 2 indicates a benign finding. BI-RADS 3 is used for a likely benign lesion, in which case a short observation interval is usually chosen instead of immediate biopsy. [26]

BI-RADS 4 indicates a suspicious finding for which tissue testing should be considered. The category is traditionally divided into 4A, 4B, and 4C: the estimated range of malignancy probability increases from greater than 2-10% in 4A to greater than 10-50% in 4B and greater than 50-less than 95% in 4C. These are probability ranges, not individual patient-specific probabilities. [27]

BI-RADS 5 indicates an image highly suspicious for cancer, with an expected probability of malignancy of at least 95%, but even here a definitive diagnosis requires morphological confirmation. BI-RADS 6 indicates that cancer has already been proven by biopsy. [28]

How to read BI-RADS

BI-RADS	Meaning	What usually happens next
0	The research is still incomplete.	Additional images/comparison needed
1	Negative	Further tactics according to the clinical situation
2	Benign finding	Routine observation
3	Probably benign	Typically short visual inspection interval
4A	Low but real suspicion	Usually a biopsy
4B	Moderate suspicion	Biopsy
4C	High suspicion	Biopsy
5	Very high probability of malignancy	Rapid morphological confirmation
6	The cancer has already been confirmed by biopsy.	Treatment planning

[29]

BI-RADS 4 or 5 - is it already cancer?

No. BI-RADS 4-5 represents a suspicion based on imaging, not a definitive diagnosis. BI-RADS 4 includes a very wide range of probability, so a significant proportion of category 4A lesions are found to be benign after biopsy.[30]

Even BI-RADS 5 remains a formal radiological category. The image is highly characteristic of a malignant tumor, but without obtaining tissue, it is impossible to reliably determine the histological type, estrogen and progesterone receptors, human epidermal growth factor receptor 2 status, and other characteristics necessary for treatment. [31]

Therefore, the standard next step for a suspicious lesion accessible for ultrasound is usually a core needle biopsy—an image-guided, thick-needle biopsy. This allows for obtaining tissue fragments for a comprehensive pathological and biomarker evaluation. [32]

Is it possible to accurately determine whether a tumor is malignant using an ultrasound?

No. Ultrasound assesses probability but does not replace histology. Certain combinations of features are highly associated with malignancy, but benign and malignant lesions overlap significantly in appearance. [33]

This explains the very principle of BI-RADS: the radiologist doesn't write "it's cancer" just because a nodule is hypoechoic or irregular. They integrate shape, orientation, borders, echotexture, posterior acoustic features, associated changes, and the clinical context to assign a final category. [34]

A definitive diagnosis requires pathological examination. Even modern artificial intelligence and radiomics methods, which demonstrate high rates of differentiation between benign and malignant nodules in studies, still do not allow for the abandonment of the standard BI-RADS approach and biopsy of suspicious findings. A 2026 meta-analysis found good average diagnostic performance of ultrasound radiomics, but highlighted significant heterogeneity across studies and the risk of overestimation. [35]

Can an ultrasound miss breast cancer?

Yes. A negative ultrasound does not rule out all types of breast cancer. The possibility of a missed scan depends on the tumor type, its size, the structure of the breast, the examination technique, and the specialist's experience. [36]

A particularly important limitation is microcalcifications. Some early tumors, primarily ductal carcinoma in situ, appear on mammography as clusters of suspicious microcalcifications without a well-formed nodule. Ultrasound is significantly less suitable for their initial detection and assessment of their extent. [37]

Modern equipment can detect some calcified lesions, especially if there is adjacent hypoechoic tissue or a nodule. This is useful, for example, for performing ultrasound-guided biopsies. However, the absence of ultrasound changes in suspicious mammographic calcifications does not invalidate the mammographic finding and is not a reason to refuse a biopsy. [38]

Invasive lobular carcinoma can also be difficult to visualize due to its diffuse, infiltrative growth. Therefore, if clinical findings, mammography, and ultrasound do not correlate, the physician may use magnetic resonance imaging. [39]

BI-RADS v2025 introduces more formalized handling of non-nodular ultrasound findings, reflecting the evolution of the method: cancer does not always form a classic “lump” on a sonogram. [40]

If the ultrasound is normal, but the lump remains

A normal ultrasound should not automatically conclude the diagnosis if the physician considers the mass itself clinically suspicious. Current ACR Criteria explicitly emphasize the need to compare physical and radiological findings. [41]

When combining normal or benign mammography and ultrasound, the negative predictive value is very high - over 97% in published series. This indeed allows, in many cases, to safely reassure the patient if the clinical examination also does not raise serious suspicion. [42]

However, the principle changes if the physician palpates a hard, fixed, or clearly suspicious lesion that is not explained by imaging. In such a situation, negative imaging should not preclude a biopsy or further specialized examination. [43]

This is where the important concept of clinical-imaging concordance—the agreement between the clinical and radiological images—comes into play. The goal is not simply to obtain a "good ultrasound," but to ensure that an explanation has been found for the specific area that is causing clinical concern. [44]

Ultrasound or mammography: which is better for breast cancer?

These methods generally do not compete with each other, but rather complement each other. Mammography is better suited for mass screening and calcification assessment, while ultrasound is particularly useful for targeted nodule characterization and for working with dense glandular tissue. [45]

Mammography provides an overview of both breasts and can detect very early calcific changes that may not be visible on ultrasound. This is why conventional ultrasound is not a universal substitute for mammography in women of screening age. [46]

The strength of ultrasound is the ability to examine a specific area in real time, change the angle of the probe, assess the boundaries of the node, and immediately use the same method to guide the needle. Ultrasound does not use ionizing radiation. [47]

In dense breasts, mammography loses some sensitivity due to the "masking" effect of dense glandular tissue. Supplemental ultrasound can detect some mammographically hidden tumors, but it also increases the rate of false-positive findings and additional biopsies. [48]

The European Society of Breast Imaging recommends that for women with extremely dense breasts in the appropriate age range, additional magnetic resonance imaging should be considered as a more evidence-based option; if this is not available, ultrasound may be used as an alternative, although its additional diagnostic value is limited.[49]

The ACR, in its recommendations for supplemental screening, evaluates ultrasound as a method that may be appropriate in average-risk women with heterogeneously or extremely dense tissue, but mammography/tomosynthesis remains the mainstay of standard screening. [50]

Ultrasound, mammography and MRI

Method	Strong point	The main limitation
Mammography/tomosynthesis	Screening, microcalcifications, full breast examination	Decreased sensitivity in dense tissue
Ultrasound	Targeted node assessment, dense breast, lymph nodes, biopsy	Operator dependent, some calcifications are less visible
Magnetic resonance imaging	Very high sensitivity, prevalence assessment in specific situations	Contrast, cost, more additional finds
Histology	Establishes the diagnosis and type of tumor	Requires invasive tissue sampling

[51]

Is it necessary to have an ultrasound if my breasts are dense?

Dense breast tissue may warrant additional imaging, but there is no universal rule that "dense breasts = annual ultrasound for everyone." The decision depends on the overall risk category, availability of magnetic resonance imaging, and the screening program. [52]

The ACR rates additional ultrasound as potentially useful in average-risk women with heterogeneously dense or extremely dense breasts. For extremely dense breast tissue, magnetic resonance imaging has a higher category of usefulness. [53]

EUSOBI also prefers magnetic resonance imaging for additional screening of women with extremely dense breasts and considers ultrasound primarily as an alternative if MRI is not available.[54]

Therefore, the statement "ultrasound is better than mammography for dense breasts" is oversimplifying the situation. A more accurate statement is that density reduces the sensitivity of mammography, so some women require an additional method, the choice of which is determined by their individual risk. [55]

How does ultrasound evaluate lymph nodes?

In cases of confirmed cancer, axillary ultrasound helps evaluate regional lymph nodes and select suspicious nodes for puncture or core biopsy. This is one of the most useful functions of ultrasound in locoregional staging. [56]

The radiologist evaluates the shape of the nodule, the thickness of the cortex, the integrity of the fatty sinus, and other morphological characteristics. An abnormal appearance increases suspicion of metastatic disease, but does not confirm it. [57]

For new breast cancer and clinically suspicious lymph nodes, the ACR recommends axillary ultrasound as a rule. If the node is suspicious, ultrasound-guided biopsy may be considered for confirmation. [58]

The normal appearance of axillary nodes cannot completely exclude microscopic metastases. Therefore, ultrasound does not replace surgical staging of the sentinel lymph node in situations where it is indicated. [59]

What does an enlarged lymph node mean on an ultrasound?

An enlarged axillary lymph node does not automatically indicate metastasis. Lymph nodes can enlarge due to inflammation, infection, vaccination, and other benign causes. The morphology and clinical context are crucial. [60]

If cancer is already diagnosed, the likelihood of tumor involvement increases, so the suspicious node may be aspirated or biopsied. This allows for a more precise regional staging before surgery or the start of neoadjuvant treatment. [61]

A normal-appearing lymph node is a favorable finding, but it does not have the same diagnostic power as a negative sentinel node. Imaging evaluates the macroscopic structure, and microscopic tumor cells may not yet alter the node's appearance. [62]

How is an ultrasound-guided biopsy performed?

If a suspicious lesion is clearly visible on ultrasound, ultrasound guidance is often a convenient way to perform a core biopsy. The physician can see the needle and tumor in real time and control the position of the needle tip. [63]

Local anesthesia is typically used. Several tissue cores are removed through a small puncture and sent to a pathologist. Core biopsy is preferable to simple fine-needle aspiration in many suspicious solid lesions because it provides more tissue for histological classification and determination of receptor status. [64]

After a biopsy, a small marker clip is often placed in the area. This helps to pinpoint the location of the original tumor, especially if the lesion shrinks after systemic treatment. [65]

If a suspicious finding is visible only on mammography—for example, a cluster of microcalcifications—its absence on ultrasound does not eliminate the need for tissue diagnostics. Mammographic/stereotactic or other appropriate guidance is then used. [66]

Is it possible to determine the size of a tumor using ultrasound?

Yes, ultrasound allows for tumor size measurement, but the measured size does not always fully reflect the true pathological extent. This is especially important in cases of infiltrative growth, multiple lesions, or a significant intraductal component. [67]

Ultrasound measurements are useful for initial assessment, biopsy site selection, and follow-up. However, when planning surgery, the data are compared with mammography and, in certain situations, magnetic resonance imaging. [68]

Invasive lobular carcinoma presents a particular challenge because it spreads through the tissue in thin chains of cells and can extend beyond the visible ultrasound nodule. It is precisely with these tumors that assessment of their extent sometimes requires additional methods. [69]

Ultrasound after cancer confirmation: why is it repeated?

Following biopsy and confirmation of cancer, repeat or extended ultrasound may be used for locoregional assessment, axillary lymph nodes, planning additional biopsy, and recording baseline dimensions before treatment.[70]

If a patient is receiving neoadjuvant systemic therapy—treatment before surgery—ultrasound may be used to measure tumor changes during and after treatment. The ACR considers ultrasound a generally appropriate modality both for baseline evaluation and after initiation or completion of neoadjuvant therapy. [71]

However, a reduction or even disappearance of a lesion on ultrasound does not prove a pathological complete response. After treatment, microscopic cells may persist at the tumor site, which are not visible using imaging methods. The final pathological response is determined based on postoperative tissue analysis and appropriate treatment strategies. [72]

A 2025 systematic review found that imaging is widely used to monitor neoadjuvant therapy, but protocols and criteria for changing treatment based on imaging findings alone are not yet sufficiently standardized.[73]

Can an ultrasound show whether chemotherapy has helped?

Ultrasound can show tumor shrinkage and changes in its structure, making it a useful monitoring method. However, ultrasound alone cannot reliably determine whether all malignant cells have been destroyed. [74]

A modern meta-analysis from 2026 showed that various ultrasound imaging modalities are indeed capable of predicting pathological response to neoadjuvant therapy; contrast-enhanced ultrasound demonstrated the best results in the studies. However, this does not mean that such methods have already replaced standard pathological assessment. [75]

Newer models based on radiomics and machine learning also show promise, but a 2026 meta-analysis found a high risk of bias in most of the included studies and called the results exploratory rather than practice-changing.[76]

Doppler and elastography: can they help detect cancer?

They can provide additional information, but are not independent methods for confirming cancer. Color Doppler ultrasound evaluates blood flow, and elastography evaluates the relative stiffness of tissues. [77]

Malignant tumors often have increased vascularity or appear more rigid, but these features overlap with those of benign lesions. Therefore, they are used as additional characteristics within the overall ultrasound evaluation. [78]

BI-RADS v2025 has expanded the description of elasticity in the ultrasound portion, reflecting the wider adoption of these technologies, but the final category is still based on the integrated assessment, and a suspicious finding requires morphological confirmation.[79]

Contrast-enhanced ultrasound and quantitative ultrasound methods are being actively investigated, including for assessing treatment response, but are not yet a universal standard replacement for conventional ultrasound, mammography, magnetic resonance imaging, or biopsy. [80]

Is an ultrasound performed after breast cancer surgery?

Sometimes yes, but routine ultrasound does not replace standard mammographic surveillance after breast-conserving treatment. For asymptomatic patients after breast-conserving surgery, the ACR considers mammography or tomosynthesis generally appropriate, while ultrasound is considered a method that may be appropriate in specific situations. [81]

Ultrasound becomes especially useful if a specific new lump, localized pain, suspicious scar change, or axillary nodule appears after treatment. Then, it is no longer a routine screening, but a targeted diagnostic task. [82]

After mastectomy, routine screening ultrasound of the operated side is not generally recommended for asymptomatic patients. However, if a new palpable mass or other clinical concern is detected, the physician will order diagnostic imaging based on the specific situation. [83]

Ultrasound during pregnancy and breastfeeding

Ultrasound is especially valuable for a new lump during pregnancy and lactation because it does not use ionizing radiation and allows for rapid assessment of a specific area. [84]

In breastfeeding women under 30 years of age, the ACR recommends ultrasound as the preferred initial investigation of a palpable mass. After age 30, diagnostic mammography also becomes part of the standard evaluation and should not be automatically excluded simply because of lactation. [85]

If an ultrasound during pregnancy reveals BI-RADS 4 or 5, the pregnancy is not a reason to simply observe the suspicious tumor. The ACR considers core biopsy to be a generally appropriate next step in this situation. [86]

When an ultrasound result requires prompt further investigation

BI-RADS 4 or 5 requires further morphological diagnostics rather than simply repeating the ultrasound in a few months. [87]

A rapid evaluation is also necessary if there is a firm or growing palpable mass, skin or nipple retraction, bloody nipple discharge, or a suspicious axillary lymph node, even if the initial examination is inconclusive. In such situations, concordance between the clinical presentation and imaging is important. [88]

This is not usually an emergency situation: a cancer diagnosis requires prompt but organized referral to a breast specialist or breast unit. Emergency care is primarily needed for severe bleeding, acute severe infection, or other sudden general deterioration, not because of the BI-RADS category itself.

What to do after a breast ultrasound

The practical next step depends primarily on the final category and whether the image matches the clinical problem.

Result	What to usually do
BI-RADS 1	If there are no symptoms, follow the usual plan; if the lump persists, compare with the examination and other tests.
BI-RADS 2	Benign finding; further management based on symptoms and screening
BI-RADS 3	Short observation interval as recommended by a radiologist
BI-RADS 4	Tissue diagnostics are usually necessary
BI-RADS 5	A biopsy should be arranged quickly.
BI-RADS 6	Cancer has already been confirmed - staging and treatment plan required
Mammography is suspicious, ultrasound is negative	A negative ultrasound does not invalidate a suspicious mammographic finding.
The mass is clinically suspicious, the images are negative	Repeat clinical evaluation is required; biopsy may remain necessary

[89] [90]

What is often misunderstood

"A hypoechoic lesion is cancer." - No. Hypoechogenicity describes the ultrasound reflection, not a histological diagnosis. Benign lesions are also often hypoechoic. [91]

"If a tumor is round and has a smooth edge, it can't be cancer." - No. Some malignant tumors, particularly certain triple-negative carcinomas, may have a less typical appearance. [92]

"BI-RADS 4 means cancer." - No. It is a suspicious category that requires tissue testing. [93]

"BI-RADS 5 is already a definitive diagnosis." - Also not. The probability is very high, but the final tumor type is determined by pathology. [94]

"A normal ultrasound completely rules out cancer." - No. This is especially true for a clinically suspicious palpable mass and mammographically detected calcifications. [95]

"If your breasts are dense, an ultrasound should be done instead of a mammogram." - No. It can complement a mammogram, and if your breasts are extremely dense, additional magnetic resonance imaging plays an increasingly important role. [96]

"If the tumor disappears on ultrasound after chemotherapy, the cancer is completely destroyed." - Not necessarily. Visual complete response and pathological complete response are different concepts. [97]

Frequently Asked Questions

Can breast cancer be seen on ultrasound?

Often yes, especially if the cancer forms a solid mass. However, some tumors and ductal carcinoma in situ may be subtle or may not have a typical ultrasound nodule at all. [98]

What color is cancer on ultrasound?

Ultrasound does not show colors like a regular photograph. On standard B-mode, a suspicious tumor often appears darker—hypoechoic—than surrounding tissue. [99]

What are the edges of cancer on ultrasound?

More often, suspicion is raised by fuzzy, angular, microlobulated, or spiculated margins. However, no single margin type provides a definitive diagnosis. [100]

What does "vertical orientation" or "taller than wider" mean?

This means that the lesion grows non-parallel to the skin and crosses normal tissue planes. This sign increases suspicion of malignancy. [101]

Can cancer be BI-RADS 3?

Rarely, yes—no imaging system is infallible. Therefore, BI-RADS 3 requires observation and should only be used when the morphology is truly consistent with a likely benign finding. [102]

Which is more dangerous - BI-RADS 4A or 4C?

4C corresponds to a significantly higher radiological probability of malignancy. However, 4A also usually requires biopsy because the risk exceeds the "probably benign" category. [103]

If the ultrasound is BI-RADS 5, is a biopsy necessary?

Yes. A high probability of cancer does not eliminate the need to obtain tissue to confirm the diagnosis and determine the biological characteristics of the tumor. [104]

Can a mammogram detect cancer that an ultrasound can't?

Yes. This is particularly common with some suspicious microcalcifications and ductal carcinoma in situ.[105]

Can an ultrasound detect cancer that can't be seen on a mammogram?

Yes, this is possible, especially with dense breast tissue and some palpable lesions. [106]

Is an ultrasound necessary after confirmed cancer?

Often yes. It can be used to evaluate the primary tumor, axillary nodes, additional lesions, and to guide biopsy.[107]

Can ultrasound detect metastases in the axillary lymph nodes?

It may detect suspicious changes, but definitive confirmation of metastasis can usually only be achieved by tissue examination. [108]

Is it possible to find out the stage of cancer using an ultrasound?

Not completely. Ultrasound provides information about the local tumor and regional nodes, but the final stage is determined based on pathology data, lymphatic status, and other studies as indicated. [109]

Is it necessary to have an ultrasound every year after cancer treatment?

Not for everyone. After organ-preserving treatment, mammography usually remains the basis for visual monitoring, and the need for additional ultrasound depends on the individual situation. [110]

Is there any harm from frequent ultrasounds?

The method does not use ionizing radiation. However, the medical problem with excessive testing is not the radiation, but false positives, repeat examinations, and unnecessary biopsies. [111]

Key points from experts

Mary S. Newell, MD, FACR, FSBI, is a professor and breast imaging specialist at Emory University and chair of the ACR BI-RADS Committee. Her professional profile highlights her expertise in breast imaging, and in the ACR BI-RADS v2025 submission, she explains the central role of standardized terminology and a single summary category for communicating clinically understandable results and recommendations. [112] [113]

Ritse M. Mann, MD, PhD, is a professor of mammary radiology at Radboud University Medical Center, a breast/interventional radiologist, and chairman of the EUSOBI Scientific Committee. In a 2026 Radboud publication, he notes the practical power of ultrasound as a targeted method for symptom assessment: images can be obtained directly at the site of complaint in real time. In screening, he views ultrasound more as a complementary or alternative method where mammography or magnetic resonance imaging are limited. [114]

Michael Fuchsjäger, MD, is a professor of radiology and head of the Department of Radiology at the Medical University of Graz. He is president of the European Society of Breast Imaging (ESBI) and serves on the board for the period 2024–2026. His expertise includes breast imaging and interventional procedures. The current EUSOBI guidelines, prepared by a European expert group, emphasize a multimodal approach to screening: the choice between mammography, magnetic resonance imaging, and additional ultrasound depends on individual risk and breast density. [115] [116]

What has changed in breast ultrasound in recent years?

The major practical update is BI-RADS v2025, released by ACR in December 2025. This is the first major update to the system since the fifth edition in 2013. The ultrasound section has received more modern terminology and additional features consistent with today's equipment capabilities. [117]

One notable change is a more formal consideration of non-nodular findings. Previously, ultrasound classification was largely based on the characteristics of the "mass," although ductal carcinoma in situ and infiltrative tumors may not form a classic nodule. [118]

The update also expanded the description of elasticity and lymph nodes. This does not change the basic principle of BI-RADS: imaging determines the level of suspicion and the subsequent route, while the final oncological diagnosis remains morphological. [119]

Contrast-enhanced ultrasound, automated volumetric scanning, quantitative ultrasound, radiomics, and artificial intelligence are all developing. Studies in 2025–2026 show promising diagnostic results, but methodological heterogeneity and insufficient external validation do not yet allow them to replace standard imaging and biopsy. [120]
[121]

Key points about ultrasound for breast cancer

Ultrasound is a very important, but not a stand-alone, test for cancer. It is particularly useful for assessing palpable lesions, clarifying mammographic findings, examining dense tissue, regional lymph nodes, and performing biopsies. [122]

The most suspicious features are irregular shape, unclear or spiculated margins, non-parallel orientation, architectural deformation, and some associated changes. However, no single feature equals a diagnosis. [123]

BI-RADS 4 or 5 usually means a biopsy is needed. BI-RADS 6 means the cancer has already been confirmed morphologically. [124]

A negative ultrasound does not invalidate a clinically suspicious mass or a suspicious mammographic finding. This is especially important for calcifications, some forms of ductal carcinoma in situ, and infiltrative tumors. [125]

The most helpful question after an ultrasound isn't "Does it look like cancer?" but rather: what is the final BI-RADS category, does the finding match a palpable area, and is a biopsy or further imaging required. These three factors determine the appropriate next step.