Breast Imaging Reporting Data System (BI-RADS)
In 1992, the American College of Radiology published a guiding document: Breast Imaging C Reporting And Data System (BI-RADS), which was subsequently revised three times and by 2003 not only guided mammography diagnosis (4th edition), but also the addition of ultrasound and MRI diagnosis. The standardization of the diagnostic reports of all normal and abnormal imaging conditions of the breast as a whole organ, the use of uniform terminology, standard diagnostic categories and examination procedures, allows radiologists to have rules to follow in their diagnosis, and also strengthens the coordination and tacit understanding between the radiology department and other relevant clinical departments, so that the clinical treating physicians know what to do next once they read the radiologists’ reports.
Note that the word Category should not be translated as “level”, but as “class”.
The BI-RADS evaluation is divided into an Assessment is Incomplete (Category 0) and an Assessment is Complete C Final Categories (Categories 1-6, Categorie 1, 2, 3, 4, 5 and 6). Indeterminate categories require further imaging, such as additional x-ray projection of the body, comparison of old films, ultrasound or MRI (note: infrared thermography or CT is not recommended). Once the additional imaging has been performed, the final category evaluation should be completed and the content of these imaging studies should be integrated to arrive at a comprehensive diagnostic evaluation classification.
The Mammography Quality Standards Act (MQSA) requires a single analysis report for mammography examinations. The hospital or clinician wishes to provide the BI-RADS classification for each breast separately, which is mentioned in the Diagnostic Findings section or the Diagnostic Description section of the report. And provide a single overall diagnostic report, expressing the BI-RADS classification at the end of the entire report. Of course, the overall final report should be based on the presence of the most worrisome things. For example, if one breast is noted as a probable benign finding and the contralateral breast is suspected of having a malignant lesion, the overall diagnostic report should be recorded as “BI-RADS Category 4 (suspicious for malignancy)”. Similarly, if one breast requires immediate additional evaluation (e.g., the patient cannot wait for ultrasound) and the contralateral breast may have a benign finding, the overall classification should be “BI-RADS category 0, indeterminate”.
The clinical finding of a lesion with a negative image is a question that many hospitals are puzzled by. The final evaluation of the diagnostic report should be based on the imaging findings. When the interpretation of the imaging findings is influenced by the clinical findings, the final evaluation should consider both aspects in a holistic manner. Clinical findings should be carefully described in the report.
Category 0: Need Additional Imaging uation and/or Prior Mammograms for Comparison.
Category 0 is used after routine mammography. Further diagnostic evaluation (e.g., additional projection positions or ultrasound) or recall of old films for analysis is required for a limited time. Contrast of old films may reduce the need for patient recall. However, controls are not always necessary (Frankel SD, 1995; Thurfjell MG, 2000). In the absence of any findings, prior photographs are helpful in only about 3 or 2% (35/1093) (Bassett LW, 1994). Only mammograms identified as having some alteration requiring comparison of older films are classified as category 0. This often includes limited asymmetric changes that may represent normal variation or radiographs showing well-margined masses that may have been present on prior images. If, however, there are no older films to compare, then further workup (such as additional x-rays and/or performing ultrasound) is warranted. In our country, some women with less fatty breasts, abundant parenchyma and lack of natural contrast in the breast tissue also require further examination using other imaging methods (e.g. ultrasound, MRI) and can also be evaluated as Category 0.
Category 1 (Category 1): Negative.
Mammography shows clear breast structures without lesions showing. Note that what is often used in our country as so-called cystic hyperplasia, lobular hyperplasia, and adenopathy (collectively referred to as fibrocystic changes or dysplasia) are all classified in this category according to the BI-RADS description. A clinically detected mass with limited asymmetric changes, despite a final diagnosis of sclerosing adenopathy, cannot be classified in this category and may be classified in category 3 or 4A. Intramammary lymph nodes and anterior axillary lymph nodes showing a hypodense lymph node gate (lateral view) or a central hypodensity (axial view of the lymph node gate) are considered normal lymph nodes and are classified as Category 1.
Category 2 (Category 2): Benign Finding
Definite benign breast masses (e.g. fibroadenoma, fibrolipid adenoma, lipoma, simple cyst, cumulus lactis cyst, cumulus oilus cyst), and definite benign calcifications (e.g. annular calcifications, short strips of calcifications with clear borders, coarse speckled calcifications, sparse and relatively single sized dotted calcifications, crescent-shaped sedimentary calcifications, etc.) are all considered to be in this category. However, clear margins of the mass are not a necessary condition to exclude malignant lesions, and in women older than 35 years of age, attention should be paid to the consultation and recall of old films for comparison or follow-up to observe their changes, and therefore may be evaluated as Category 0 or Category 3, respectively.
Category 3 (Probably Benign Finding C Initial Short-Interval Follow-Up Suggested, Initial short-term follow up (usually 6-month) examination, Category 3 (Probably Benign Finding C)
Category 3 (Probably Benign) was retained, and its findings were almost certainly benign. It must be emphasized that this category is not an indeterminate type, but for mammography it has a less than 2% chance of being malignant (i.e. almost always benign). The presentation is gradually recognized, based on images with or without previous screening results. Evaluation with additional projections and/or ultrasound of the breast in other orientations requires a category 3 (probably benign). This type of lesion includes well-defined masses that cannot be visualized on conventional radiographs (unless they are cysts, intramammary lymph nodes, or other benign lesions), limited asymmetric changes with thin sections on spot compression films, and fine clusters of calcifications. Short-term follow-up is performed using unilateral radiographs 6 months after routine mammographic findings. If there is no change in the lesion, a further bilateral breast follow-up at 6 months is recommended (i.e., 12 months after the initial finding). If no other suspicion is observed at the second bilateral breast follow-up, a category 3 is reported and a typical post-12-month bilateral breast follow-up (i.e., 24-month follow-up after the initial examination) is recommended. If the next follow-up (24th month follow-up) still reveals no change, the final assessment may be a category 2 (benign) or of course a category 3 (probably benign) in conjunction with clinical caution. According to the literature (Sickles EA, 1995) after 2-3 years of stabilization, the final diagnosis may change to category 2 (benign), but still requires follow-up and, if necessary, magnification photography.
Perhaps a less experienced physician would insist on a smaller confined asymmetric change, thus defining it as a category 3. The more experienced physician with 6, 12, or 24 month follow-up may decide that this change is a normal variant and for this reason determine it as a category 1 (negative).
Category 3 may be immediately biopsied for reasons such as clinician or patient fear of tumor and unwillingness to follow up, and in these cases the final diagnostic assessment classification should be based on the risk of malignancy rather than on the management offered. Lesions that are judged by ultrasound as possibly benign include complex cysts that cannot be palpated. The malignancy rate of non-palpable ovoid hypoechoic nodules that cannot be distinguished from complex cysts has been reported to be less than 2%. Clusters of microcysts without discrete solid components may also be rated as category 3.
Proper classification of category 3 requires review of the physician’s practice. The malignancy rate in such cases should be less than 2%. For ultrasound, the malignancy rate should also be less than 2%, but this has not been confirmed in a wide range of articles. For MRI, cases classified in this category have only been followed for a short period of time and their malignancy rate needs further study.
Category 4 (Category 4): Suspicious Abnormality C Biopsy Should Be Considered.
Category 4 is used to indicate interventional radiology procedures that require biopsy from complex cyst aspiration to polymorphic calcification. Many units subcategorize the 4 categories to account for differences in interventional management and malignancy risk. This is done using a receiver-operating characteristic curve (ROC curve) analysis, which is subject to greater clinical scrutiny to help clinicians and radiologists. 4 categories are divided into three subcategories to help achieve these purposes.
Category 4A: Finding needing intervention with a low suspicion for malignancy.
Category 4A is used to represent lesions that require intervention but are less malignant. The pathology is not expected to be malignant, and routine follow-up for 6 months after a benign biopsy or cytology result is appropriate. This category includes some solid masses with palpable, partially well-defined margins, such as ultrasound suggestive of fibroadenoma, palpable complex cysts, or suspicious abscesses.
Category 4B: Lesions with an intermediate suspicion of malignancy.
Category 4B includes lesions with an intermediate suspicion of malignancy. The correlation between radiological diagnosis and pathological findings is close to the same. In this case, benign follow-up depends on this consistency. A partially well-defined, partially indistinct mass that may be a fibroadenoma or fatty necrosis is acceptable; however, papilloma requires excisional biopsy.
Category 4C: Findings of moderate concern, but not classic for malignancy.
Category 4C lesions indicate moderate concern, but not classic for malignancy as in category 5. These include, for example, solid masses with poorly defined borders, irregular shape, or new microscopic polymorphic clusters of calcifications. Such pathologic findings are often malignant.
These subcategories of Category 4 should encourage pathologists to proceed with further analysis of lesions reported as benign in Category 4C, and clinicians should be made aware of the need for follow-up review of cases diagnosed as Category 4 but reported as benign on biopsy.
Category 5: Highly Suggestive of Malignancy C Appropriate Action Should Be Taken
Category 5 is used to express lesions that are almost certainly breast cancer. In earlier versions of BI-RADS, when puncture biopsies to obtain histologic or cytologic diagnoses were not widely available, Category 5 predicted that lesions would eventually be treated without prior tissue specimens. Now, specimens with such findings must be retained to detect typical breast cancers with a 95% probability of malignancy. Irregularly shaped masses with burrs, thin strips of calcifications in a segmental or linear pattern, or irregularly shaped masses with burrs and accompanying irregular and polymorphic calcifications are classified as category 5. Normative biopsies without typical malignant lesions are classified as category 4.
Category 6: Known Biopsy-Proven Malignancy C Appropriate Action Should Be Taken
Category 6 is a new category added to describe cases with biopsy-proven breast cancer but with only limited prior treatment (e.g., surgical excision, radiation, chemotherapy, or mastectomy). Unlike BI-RADS categories 4 and 5, category 6 does not require interventional management to determine if the lesion is malignant. A second diagnosis found in a previous specimen and shown to be malignant, or to detect the effects of neoadjuvant chemotherapy administered prior to surgery can be assessed as category 6.