Breast cancer: The appearance as delineated by whole breast water-path ultrasound scanning

J Clin Ultrasound 10:313-322, September 1982

Breast Cancer: The Appearance as Delineated by Whole Breast Water-Path Ultrasound Scanning

Daniel B. Kopans, MD, Jack E. Meyer, MD, and R. Ted Steinbock, MD

Abstract: The sonographic appearance of 130 breast carcinomas imaged by a dedicated breast scanning system is reviewed. Five separate categories are identified and examples of each category with corresponding xeromammograms are presented. Indexing Words: Breast carcinoma . Breast ultrasound

Early ultrasonic evaluation of the breast required direct application of the transducer which was not ideal because pressure from the transducer can displace masses from the path of the sound beam. This problem was addressed by water-path scanning units in which the sound is transmitted through a water bag placed on the breast. More recently, dedicated whole breast ultrasound units have been developed in which the patient is ex- amined in the prone position with the breast immersed in water and the transducer located at a fixed distance from the breast. Our experience with one such device suggests that there is a range of appearances that may characterize breast cancer and expands the criteria previously described. An awareness of this spectrum is crucial when evaluating the breast sonographically.

MATERIALS AND METHODS

A total of 130 biopsy-proven malignant breast lesions visualized by ultrasound from October 1979 through July 1981 were reviewed. The scans were obtained with an automated real-time whole breast water-path scanning unit that was a pro- totype of the SMV-120 Sonic Mammographic ViewerTM developed by the Special Research Group of Technicare Corporation.* The system utilized a 3.2-MHz large aperture sector scanning transducer, and the scans were performed

*Technicare Corporation, 90 Inverness Circle East, Engle- wood, CO 80112.

From the Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston. Manuscript re- ceived December 1, 1981; revised manuscript accepted April 20,1982. For reprints contact Daniel B. Kopans, MD, Depart- ment of Radiology, Massachusetts General Hospital, Boston, MA 02114.

@ 1982 John Wiley & Sons, Inc. 0091-27511821070313-10 $01 .OO

with the patient in the prone position with the breast immersed in a body-temperature water bath. The breast was compressed against the chest wall with a clear polyurethane membrane producing a more perpendicular angle of the incident sound to the tissue planes of the breast. This appears to improve visualization of many lesions by compressing surrounding normal tissue. The scans were routinely performed in the sagittal plane, and although transverse and coronal sec- tions were frequently obtained, our discussion will be limited to the routine sagittal views. All patients had xeromammograms performed on the same date as the ultrasound examination.

RESULTS

Based on measurements obtained from the x-ray studies and pathologic specimens, the malignant lesions ranged in size from 6 mm to diffuse in- volvement of the breast. The average diameter of the lesions was 2.6 cm.

Our analysis suggests that breast cancer as imaged by this type of unit can be divided into five major categories:

Category 1 -Acoustic shadowing (451130) -35%: This is a category of lesions that has been previously described as the classic appearance of breast cancer by ultrasound. 1,2 These lesions have anterior surfaces that scatter and at- tenuate the sound completely and prevent the return of any echoes from the retrotumoral tissues (Fig 1). Such areas of shadowing were identified in 45 patients (35%).

Category 2-Hypoechoic masses sharply defined by the surrounding parenchyma (331130)-25% : Although sharply defined margins have been

313

314 DANIEL B. KOPANS ET AL

FIGURE 1. A: The sound is completely blocked causing a dense shadow behind the anterior surfaceofthe pathologically proven 2.5-cm infiltrating ductal carcinoma. B: Xeromammogram of the lesion.

identified as a benign characteristic,2 hypoechoic cancers with margins sharply delineated by the surrounding parenchyma were seen in 33 (25%) patients. These lesions demonstrated a very abrupt zone of transition between the abnormal tissue and normal surrounding parenchyma. In 20 (15%) patients, the ultrasound image demonstrated a surrounding wall that was more echogenic than the adjacent parenchyma (Fig 21, and in 15 patients there was actual retrotumoral acoustic enhancement (Fig 3). In several instances lesions could have been mistaken for cysts; however, the random low-level internal echoes ruled out such errors.

Category 3 -Hypoechoic masses with ill-defined margins (211130) -1 6%: Hypoechoic areas with ill-defined irregular margins that merge gradually into the surrounding parenchyma with a wide zone of transition between the normal parenchymal texture and the lesions were visualized in 21 (16%) patients (Fig 4). These lesions were frequently difficult to dis- tinguish from the normal hypoechoic varia- tions and echo texture of the breasts, but were more apparent when contrasted with the corresponding region of the opposite breast.

Category 4 -Architectural asymmetry (61130)- 5%: Six lesions were visible because of an architectural asymmetry (Fig 5). No mass was demonstrable sonographically, but the fine lines of Cooper’s ligament were disorganized and thickened. In addition, the architecture was not symmetrical with the contralateral

breast suggesting the presence of a lesion. Car- cinoma was visible on all six mammograms.

Category 5-Echogenic focus without shadowing (21130)-2%: It has been our experience that clustered microcalcifications routinely are not visible by ultrasound. However, two lesions presented as echogenic foci without shadowing. These areas correspond to clustered microcalcifications visible xeromammographically

JOURNAL OF CLINICAL ULTRASOUND

WATER-PATH SCANNING FOR BREAST CANCER 315

FIGURE 2. A: Sharply defined mass with margins that appear separate from the surrounding parenchyma (arrows). There is no posterior shadowing. Biopsy revealed a 1.7-cm infiltrating ductal carcinoma. B: Xeromammogram of the lesion (arrows).

malignancy, 23 tumors (17%) were found in patients in whom large volumes of the mammary parenchyma were refractory to the penetration of sound. Pathologically, these lesions varied in size from 1.5 cm to extensive breast infil- tration. Sonographically, no discrete clearly defined mass could be seen, but the breast tissue was remarkably refractory to the penetration of sound in spite of flattening the tissue against the chest wall and increasing the sonic power of the system. In most cases the shadow was much larger than what could be accounted for by the size of the tumor alone. Although the phenomenon may be totally unrelated to the presence of a malignant process and these might be considered false-negatives, no corre- lation was possible with any similar factors. It was seen in women with varying breast size and in all four types of breast parenchyma, not just the diffusely fat-infiltrated breast. It is our strong belief that patients with breast parenchyma that is refractory to the penetration of sound require careful evaluation (Fig 7).

DISCUSSION

Because this was a retrospective analysis, no at- tempt was made to evaluate the accuracy of ultrasound in the detection of breast cancer relative to other modalities. It was apparent, however, that ultrasound cannot stand alone as a screening modality. Our experience demonstrates that there is a spectrum of appearances that breast cancer can assume and it is important to be aware of this variation so that accurate interpretation of whole breast scans can be made.

A classic irregular hypoechoic area with dis- tal shadowing has been described by several

and were subsequently proven to be related to a malignant process (Fig 6). There was no associated mass on either the ultrasound or the xeromammogram.

The High Attenuation Breast: Although this cannot yet be considered a separate category of

VOL. 10, NO. 7, SEPTEMBER 1982


FIGURE 3. A: 1.5 cm mass in the upper inner right breast with sharply defined margins and posterior acoustic enhancement (curved arrow). 8: The dense mammary parenchyma obscures the 1.5-cm carcinoma on the xeromammogram.



FIGURE 4. A: Category 2A-Ill-defined hypoechoic mass with margins fading into the surrounding tissues (arrows). B: The dense mammary parenchyma obscures the intraductal carcinoma on the xeromammogram.



FIGURE 5A: Architectural distortion with thickening of Cooper's ligament and disruption of the subcutaneous tissues (arrow). Biopsy revealed a 2.0-cm infiltrating ductal carcinoma.

FIGURE 58: Ultrasound of the unaffected breast demonstrates the normal parenchymal architecture in the corresponding area.

observer^.^-^ In our series this type of appearance was seen in 35% of the cases. An unexpected finding was that 25% of the cancers in our series appeared as relatively well-defined masses (Cate- gory 2). Fifteen of these actually demonstrated enhanced sonic transmission, a finding previously ascribed to benign lesions such as cysts and fibroadenomas, and an occasional medullary carcinoma. In order to avoid misdiagnosis, the inter- preter must adhere to strict criteria. All of these masses were hypoechoic relative to the surrounding parenchyma, but none were totally anechoic. It has been our experience that the presence of internal echoes is important for diagnosis, but their distribution is less useful as a diagnostic cri- terion. If any one of the classic ultrasound charac- teristics of a cyst is not present, the level of suspicion of malignancy increases.

Breast architectural asymmetry is well known in x-ray mammography and is equally important in breast ultrasound evaluation. Although the

breasts may not be absolutely equal in size, there is an important symmetry between corresponding volumes of tissue. Many of the tumors in this series were more readily apparent because the architecture in the region of the tumor differed from the architecture in the corresponding area in the contralateral breast. This was especially true in Categories 3 and 4. Several abnormalities may occasionally be detectable only as areas of asymmetry. Thus it is important to not only evaluate each breast individually, but also together as a symmetrical organ system.

The high attenuation breast is the subject of ongoing evaluation. It is well known that the uncompressed breast as visualized by water-bath units may have a dense subareolar shadow that appears to conform to the parenchymal cone (Fig 8A). In the uncompressed breast, this type of drop out is most directly a result of the angle of incident sound in relation to the structures of the parenchymal cone. This obtuse angle causes scat-



FIGURE 6. A: There is a localized nonshadowing echogenic focus (arrow). Pathology revealed an intraductal comedocarcinorna. B: Xerornarnrnograrn demonstrates clustered rnicrocalcifications without a mass (arrows).

tering , refraction, and nonpenetration of the sound into the breast parenchyma. In the normal patient, compressing the breast toward the chest wall (Fig 8B) permits complete visualization of the parenchymal tissue. In the high attenuation breast category, compression and increasing sonic power did not improve the visualization of the deep structures. Contrary to expectations, all these women did not have dense parenchyma as imaged on x-ray mammography; nine had nearly total fatty replacement (Wolfe’s N-1 category) and four had minimally visible ducts (Wolfe’s P-1 category). There were seven P-2 patients and three with a dense D-Y pattern. In addition, the breasts in this category varied in size. It is well documented that malignant breast tissue can at- tenuate sound more than normal tissue or benign lesion^.^*^ The amount of attenuation appears to correlate with the amount of connective tissue within the tumor.’ It is well known that breast cancer may be a “field, phenomenon as evidenced by multicentric simultaneous lesions and contralateral synchronous tumors. It is clear also that ultrasound parenchymal patterns do not al- ways correlate with x-ray patterns and that it is possible that subtle diffuse alterations in breast parenchyma associated with a malignant process may change the sonic attenuation of the tissue be- fore altering the x-ray attenuation and prior to a lesion becoming palpable. Further studies of these 23 patients with high attenuation breasts may reveal a higher rate of malignancy in the contralateral breast. Independent of the explana- tion and allowing for the possibility that these results may be merely true false-negatives, it is crucial to note that if there are portions of the



breast that are not imaged satisfactorily by ultrasound, the patient’s clinical status must be considered suspicious and further investigation is advised.

Some other signs of malignancy have not been discussed in detail because they usually represent late changes in breast cancer, such as skin thickening (Fig 9) and retraction (Fig 10). Our experience suggests that skin thickening is detected as accurately by ultrasound as by xeromammog-

FIGURE 7. A: The malignant lesion is not clearly defined due to the high attenuation of sound by the breast parenchyma. Biopsy revealed a 2.0-cm infiltrating ductal carcinoma. B: Xeromammogram of the lesion !arrows).

r a ~ h y . ~ Skin retraction is usually evident clini- cally when it is visible sonographically.

We would emphasize that in our experience, there were no malignant changes detectable by ultrasound that were not either palpable or visible by mammography. Ultrasound is a very useful adjunct to increase the level of suspicion, but it cannot stand alone as a screening technique.

Improvements in scanning techniques and equipment will no doubt result in more refined



FIGURE 8. A: There is an intense subareolar shadow in the uncompressed parenchymal cone secondary to the oblique angle of the incident sound. B: The same breast with compression against the chest wall by a polyurethane membrane. The scan was taken in the same plane of the nipple and demonstrates satisfactory imaging of the parenchyma because of a more perpendicular angle of the incident sound.

FfGURE 9. Skin thickening secondary to dermal lymphatic involve- ment by carcinoma. The thickened skin is delineated by the specular epidermal reflection and the relatively specular reflection of the dermal subcutaneous fat interface (arrows).

FIGURE 10. Retraction of the skin producing a concave segment secondary to an infiltrating malignant process (arrow).



characterization of malignant lesions. However, at present it is incumbent upon those using scanning breast ultrasound devices to be aware of the spectrum of appearances that breast cancer may assume so that this modality can contribute to the management of malignant disease.

REFERENCES

1. Cole-Beuglet C, Beique RA: Continuous ultrasound B-scanning of palpable breast masses. Radiology 117:123, 1975.

2. Kobayashi T: Gray-scale echography for breast cancer. Radiology 122:207, 1977.

3. Teixidor HS, Kazam E: Combined mammographic- sonographic evaluation of breast masses. A J R 128:409, 1977.

4. Yokoi H, Tatsumi T, Ito K, et al: Comparison of the ultrasonic simultaneous tomogram with gross and microscopic findings of the mammary tumors. In Proceedings of the 25th Meeting of the Japan Society of Ultrasonics in Medicine, Vol. 25, Tokyo, 1974, p 153.

5. Calderon C, Vilkomerson D, Mezrich R, et al: Dif-

ferences in attenuation of ultrasound by normal, benign and malignant breast tissue. J Clin Ultrasound 4:249, 1976.

6. Cole-Beuglet C, Kurtz AB, Rubin CS, et al: U1- trasound mammography. Radio1 Clin North Am 18(1):133, 1980.

7. Wolfe JN: A study of breast parenchyma by mammography in the normal woman and those with benign and malignant disease. Radiology 89:201, 1967.

8. Kobayashi T: Diagnostic ultrasound in breast cancer: Analysis of retrotumorous echo patterns cor- related with sonic attenuation by cancerous connective tissue. J Clin Ultrasound 7:471, 1979.

9. Kopans DB, Meyer JE: The double line of skin thickening on sonograms of the breast. Radiology 141:485, 1981.

ACKNOWLEDGMENTS

We gratefully acknowledge the support and work performed by Judy Aldrich, Jean Crowley , Irene MacGillivray, Cynthia Puryear, Catherine Repko, and Roberta Singer.


Documents

Breast cancer: The appearance as delineated by whole breast water-path ultrasound scanning