Incident Angle of the Plunging Artery of Breast Tumors

Incident Angle of the Plunging Artery of Breast Tumors

Yuka Kujiraoka

, Ei Ueno

, Eriko Tohno

, Isamu Morishima

, and Hiroko Tsunoda-Shimizu

72

Summary. We measured the incident angle of the feeding artery of breast tumors on color Doppler ultrasonography. Ninety-two tumors that had plunging arteries (21 fibroadenomas and 71 breast cancers) were retrospectively evaluated. Breast cancers were divided into three types [accentuating type (ACC), 25; intermediate type (INT), 35; and attenuating type (ATT), 11] by posterior echo. Color Doppler ultrasonography was performed using an HDI 5000 (ATL Ultrasound, USA) with a 7- to 10-MHz linear probe. We measured the incident angle of the feeding artery on color Doppler imaging.

If the tumor had many plunging vessels, we measured all of them. The average incident angle of the artery of fibroadenoma was 47.5° and that of breast cancer was 17.6°.

Fibroadenoma ranged from 15° to 70° and breast cancer from 0° to 70°. In breast cancer, there were no significant differences among the three types (ACC, INT, and ATT). We concluded that the incident angle of the feeding artery adds valuable infor- mation to the color Doppler ultrasonographic diagnosis for breast tumors.

Key words. Incident angle, Breast tumor, Fibroadenoma, Breast cancer, Color Doppler ultrasonography

Introduction

Recently, morphological characteristics of tumor vessels have been evaluated by color Doppler and power Doppler imaging [1]. Experimental evidence indicates that pro- liferation and distribution of tumor vessels are linked to tumor growth pattern [2].

Malignant tumors grow rapidly and involve surrounding tissue, so the arteries plunge and penetrate into tumors. Benign tumors grow slowly and press surrounding tissue, so the arteries go around the margin of tumors [3–5]. However, sometimes we find

1

Department of Radiology, Tsukuba Memorial Hospital, 1187-299 Kaname, Tsukuba, Ibaraki 300-2622, Japan

2

Institute of Clinical Medicine, Tsukuba University, 2-1-1 Amakubo, Tsukuba, Ibaraki 305-8576, Japan

3

Department of Surgery, Tsukuba Medical Center, 1-3-1 Amakubo, Tsukuba, Ibaraki 305-8558, Japan

4

Department of Radiology, St. Luke’s Hospital, 9-1 Akashi, Chuo-ku, Tokyo 104-8560, Japan

cases of fibroadenoma that have plunging arteries. Are there any differences about the plunging pattern between breast cancer and fibroadenoma? We measured incident angle of plunging arteries of breast tumors on color and power Doppler imaging. We compared the incident angle of breast cancer with that of fibroadenoma to know the potential of incident angle to differentiate benign from malignant solid breast tumors.

Materials and Methods

Ninety-two breast tumors that had plunging arteries were evaluated; 21 were fibroade- noma and 71 were breast cancer. If the tumor had many plunging arteries we meas- ured all of them, so in total 131 plunging arteries were evaluated. Color and power Doppler ultrasonography was performed using an HDI 5000 (ATL Ultrasound, USA) with a 7- to 10-MHz linear probe. One representative color or power Doppler echogram was chosen for each tumor, and the incident angle was measured on it. We drew two lines on the point of plunging arteries. One was drawn tangential to the tumor, and the other was drawn vertical to this tangential line. The angle between this vertical line and the plunging artery ranged from 0° to 90° (Fig. 1).

The average of incident angle in breast cancer was compared with that of fibroade- noma by means of the two-tailed Student’s t test for unpaired data. With the F test, the mean of incident angle in the attenuating type (ATT) group was compared with the intermediate type (INT) group and the accentuating type (ACC) group. A P value of less than 0.05 was considered to indicate a statistically significant difference. The receiver operating characteristic (ROC) curve was constructed and the cutoff point determined.

Results

The average incident angle of fibroadenoma was 47.5° and that of breast cancer was 17.6° (Table 1). The incident angle of fibroadenoma ranged from 15° to 70° while that of breast cancer ranged from 0° to 70° (Fig. 2). The average incident angle of breast cancer is significantly lower than that of fibroadenoma. There are no significant dif- Plunging Artery of Breast Tumors 73

Line B

Line A

Incident angle Plunging artery

Fig. 1. Schematic drawing of measurement of incident angle. We drew two lines on the point

of plunging arteries, one tangential to the tumor (line A) and the other vertical to this tangen-

tial line (line B). The angle between this vertical line and the plunging artery was measured

ferences among the three groups (ATT, INT, and ACC) of breast cancer (Fig. 3). From the ROC curve, 30° was adopted for the cutoff point. At this point, sensitivity of malig- nancy is 86% and specificity is 88%.

Discussion

Previous study of the morphological features of tumor vessels has indicated that pen- etrating arteries are highly suggestive of malignancy and surrounding marginal arter- ies are suggestive of benignity [1]. Plunging arteries are frequently seen in breast cancer, but are also seen in fibroadenoma in some cases. We investigated the incident angle of plunging arteries of breast tumors on color and power Doppler imaging. We found that the incident angle of breast cancer was lower than that of fibroadenoma.

Although their range overlaps, if the cutoff point is set at 30°, the sensitivity of malig- nancy is 86% and the specificity is 88%. Incident angle seems to be useful to differ- entiate a benign tumor from malignancy. On the other hand, 4 of 31 (12%) cases were false positive at this cutoff point. In these fibroadenomas, the shape of tumors tends to be lobulated and their plunging arteries lie among the lobes; this might be the reason why the tumors have a low incident angle. Establishment of the combination of incident angle and other features increases the accuracy.

74 Y. Kujiraoka et al.

Table 1. Statistical analysis: fibroadenoma (Fa) versus breast cancer (Ca)

Number Average Range Distribution SD

Fa 31 47.5 20–70 209.7 14.4

Ca 100 17.6* 0–70 262.3 16.1

ATT 17 16.4 0–45 180.5 13.4

INT 49 17.5 0–70 299.0 17.2

ACC 34 18.2 0–50 263.4 16.2

SD, standard deviation; ATT, attenuating type; INT, intermediate type; ACC, accentuating type

*Average of incident angle of the breast cancers is lower than that of fibroadenomas (P < 0.05)

Fig. 2. Distribution of incident angle in fibroadenoma and breast cancer. Fa, fibroadenoma;

Ca, breast cancer

Conclusion

Incident angle is one of the important values in the differentiation of breast tumors on color and power Doppler imaging. Establishment of the combination of incident angle and other features would be useful in daily practice.

References

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3. Weind KL, Maier BCF, Rutt BK, et al. (1998) Invasive carcinomas and fibroadenomas of the breast: comparison of microvessel distributions—implications for imaging modal- ities. Radiology 208:477–483

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Imaging (suppl 2 zu Band) 60:45

Plunging Artery of Breast Tumors 75

Fig. 3. Distribution of incident angle of breast cancer. ATT, attenuating type; INT, intermedi-

ate type; ACC, accentuating type