Usefulness of Depth to Width Ratio in Differentiation of Regular Invasive
Ductal Carcinoma from Fibroadenoma
Hiroko Tsunoda-Shimizu, Yasuyuki Kato, Ei Ueno, Tokiko Endo, Mitsunori Shirouzu, Ryouji Watanabe, Hideyuki Hashimoto, Yoshinari Ogawa, Tsutomu Takashima, Yasuhisa Fujimoto, Hideaki Shirai, Manabu Nagae, Noriko Unuma,
Norikazu Masuda, Norikazu Obane, Isamu Morishima, Yuka Kujiraoka, Kiyoka Omoto, and Nobuyuki Taniguchi
57 Summary.
Depth to width ratio (D/W) is the only quantitive item in seven criteria used to evaluate breast masses by the Japanese Ultrasound Society. Recent technical improvement of ultrasound is remarkable, but the usefulness of the D/W has not fully been evaluated. We reviewed prospectively the D/W estimation of breast masses by using dedicated ultrasound units in ten hospitals that belong to the Japanese Breast and Thyroid Sonology and the Japanese Ultrasound Society. The materials included 163 regular invasive ductal carcinomas (CA) and 219 fibroadenomas (FA) that were selected from consecutive cases and which were smaller than 30 mm in diameter. The mean size of CA was 17 mm and that of FA was 14.5 mm. The D/W of CA was 0.76, significantly larger than that of FA, 0.57. The larger the size of the tumor, the smaller became the D/W in both CA and FA. The D/W of these two kinds of tumors was significantly different in cases with tumors larger than 5 mm in diameter. We also reviewed the D/W of three groups divided by the posterior echoes; that is, attenuat- ing masses, no change, and accentuating. The D/W of the attenuating mass was larger than that of the other two groups. We reconfirmed that the D/W was useful in differ- entiating CA from FA.
Key words.
Breast ultrasound, Breast cancer, Fibroadenoma, Depth to width ratio
Introduction
Our title is usefulness of depth to width ratio in the differentiation of regular inva- sive ductal carcinoma (CA) from fibroadenoma (FA). The depth to width ratio (D/W) was first established by the Japanese Ultrasound Society in 1989 as a useful diagnos- tic tool in differentiating malignant from benign tumors [1, 2]. Technical improve- ment of ultrasound during the post decade is remarkable, but the usefulness of the D/W has not been fully evaluated.
The Committee of the Breast Ultrasound Criteria, Japanese Association of Breast and Thyroid Ultrasound Sonology, Department of Radiology, St. Luke’s Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan
The definition of the D/W is a division of depth by transverse diameter of the mass.
The transverse diameter is the maximum diameter of the mass on ultrasound and is measured in the direction running parallel to the skin. The depth diameter is the ver- tical length of the mass perpendicular to the transverse diameter. The measurement is performed using only the low-echoic area without the echogenic boundary echoes or halo. The purpose of this study is to evaluate the usefulness of the D/W in differ- entiation of regular invasive ductal carcinomas from fibroadenomas using dedicated units. This investigation was performed with the collaboration of ten institutes that belong to the Japanese Breast and Thyroid Sonology and Japanese Ultrasound Society.
Methods and Materials
A questionnaire was sent by e-mail to these 10 institutes. The questionnaire included patient’s age, depth and transverse diameter of the mass, final diagnosis, ultrasound units, and so on. The physicians and sonographers filled in the items of this ques- tionnaire from their results of the ultrasound examinations. The participating insti- tutes for this study are shown in Table 1.
The materials included breast masses examined during the period between January 1998 and June 1998. Masses of a size equal to or smaller than 30 mm in maximum diameter were selected. Twenty consecutive malignant lesions were selected per each institution. All benign lesions were selected during the period when these 20 malig- nant lesions were collected. The tumors that did not change in size and nature for 3 years were included as benign lesions without histological confirmation. Total number of the materials was 223 malignant cases, including 163 regular ductal carcinomas, and 313 benign cases including 219 fibroadenomas.
The ultrasound equipment used is listed in Table 2. The frequency of the trans- ducers was from 6 to 13 MHz. Multifrequency transducers were used in some insti- tutes. The scan methods were mechanical sector, electric linear, and annular array scan.
Table 1. Participating institutes
Institution Investigator
Breastopia Namba Hospital K. Shirouzu, R. Watanabe
Chiba University H. Hashimoto
Osaka City Hospital Y. Katoh, Y. Ogawa, T. Takashima Osaka City Medical Center Y. Fujimoto
Sapporo Kotoni Breast Clinic H. Shirai
St. Marianna Medical School M. Nagae, N. Unuma
Sakai City Hospital N. Masuda
Sumitomo Hospital N. Obane
Tsukuba University H. Tsunoda-Shimizu, I. Morishima Y. Kujiraoka, E. Ueno
Jichi Medical School K. Omoto, N. Taniguchi
Results
The D/W by tumor size is shown in Fig. 1. The transverse axis is tumor size divided by 5 mm and the vertical axis is the D/W. As shown here, the smaller the tumor size, the larger the D/W in both malignant and benign cases. In any tumor size, D/W of the malignant tumors was larger than that of benign tumors. This difference was sta- tistically significant in cases with tumor size smaller than 25 mm but not for cases with tumors larger than 25 mm.
The D/W of fibroadenomas and regular type of invasive ductal carcinomas is shown in Fig. 2. The D/W of FA was 0.57, and the D/W of CA was larger than 0.7 in the any type of regular invasive ductal carcinomas. Scirrhous carcinoma showed the largest D/W, 0.79; in solid-tubular carcinoma, the D/W was 0.75; and in papillotubular carci- noma, it was 0.71. The D/W of FA and invasive ductal carcinoma that were evaluated by tumor size are shown in Fig. 3. The D/W of fibroadenoma was smaller than that
Table 2. Ultrasound equipment
Manufacturer Model Frequency Scan type
Aloka SSD 650 CL 10 MHz Electric linear
1700 7.5 MHz Mechanical sector
2000 10 MHz Electric linear
GE Logiqe 500 6–13 MHz Electric linear
8.3–13 MHz Electric linear
700 MR 7.5 MHz Electric linear
Toshiba SSA 250 A 7.5 MHz Anular array
340 A 6, 8 MHz Anular array
Siemens 7.5 MHz Electric linear
Fig. 1. Depth to width ratio (D/W) ratio by tumor size
Fig. 2. D/W of fibroadenomas and invasive ductal carcinomas. FA, fibroadenoma; papitub., papillotubular; solid-tub., solid-tubular
Fig. 3. D/W of fibroadenomas (FA) and invasive ductal carcinomas. fa, fibroadenoma; pap, papillotubular; sol, solid-tubular; sci, scirrhous
of any type of carcinomas except for those smaller than 5 mm in size in papillotubu- lar carcinomas. The D/W of scirrhous carcinoma was significantly larger in tumors larger than 15 mm.
Discussion
We studied the most useful threshold in D/W to differentiate malignancy from benign lesions. The sensitivity, specificity, and accuracy in each value of the D/W are shown in Fig. 4. The larger the D/W is, the higher is the specificity but the lower is the sen- sitivity. Sensitivity and specificity cross between 0.6 and 0.7 in the D/W. The highest accuracy, 68.5%, was noted when the D/W was 0.7.
In conclusion, the D/W of malignant tumors was larger than that of benign tumors.
This difference was statistically significant in cases with tumors smaller than 25 mm.
The D/W of fibroadenoma was smaller than that of any type of invasive ductal carci- nomas of any size, except for papillotubular carcinomas smaller than 5 mm. The threshold of the D/W in malignant and benign tumors was approximately 0.7.
References
1. Tajima T, et al (1983) Longitudinal/transverse ratio of tumor echogram as a diagnostic criterion of breast carcinoma. In: Jellins J, Kobayashi, T (eds) Ultrasonic examination of the breast. John Wiley, pp 69–70
2. Tohno E, et al (1994) Diagnostic features on ultrasound. In: Ultrasound diagnosis of breast disease. Churchill Livingstone, pp 50–53
Fig. 4. Threshold of D/W
