Japanese Journal of Clinical Oncology 32:157-161 (2002)
© 2002 Foundation for Promotion of Cancer Research
Accuracy in Estimating Tumor Extension According to Mammographic Subtypes in Patients with Ductal Carcinoma In Situ
1 Breast Surgery Division and 2 Diagnostic Radiology Division, National Cancer Center Hospital and 3 Pathology Division, National Cancer Center Research Institute, Tokyo, Japan
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Background: The association between subtypes of mammographic findings and histopathological tumor extension in patients with ductal carcinoma in situ has remained unclear. The purpose of this study was to investigate the relationship between tumor extension on mammography, by stratifying four subtypes, and histopathological tumor size in patients with ductal carcinoma in situ.
Methods: This study was performed on 109 breasts with ductal carcinoma in situ. They were treated by mastectomy at our Hospital between January 1990 and December 1999. Findings on mammography were categorized as microcalcification type, spiculated type, circumscribed type or fibrocystic-change type. The microcalcification type consisted of breasts with malignant microcalcifications, regardless of the presence or absence of tumor shadow. We analyzed the relationship between tumor size on mammography in each category and histopathological tumor size. In the breasts with palpable tumors, we compared palpated tumor size and histopathological tumor size according to the mammographic subtypes.
Results: There was no statistical difference between mammographic tumor size and histopathological tumor size for each mammographic subtype (microcalcification type, P = 0.60; spiculated type, P = 0.72; circumscribed type, P = 0.055). The size of the ductal carcinoma in situ in microcalcification and spiculated type was estimated approximately by mammography. However, mammography tended to overestimate the circumscribed type. In the cases of palpable tumor, we statistically underestimated the size of ductal carcinoma in situ by palpation in microcalcification and fibrocystic-change type (microcalcification type, P = 0.0001; fibrocystic-change type, P = 0.040).
Conclusion: Mammographic categorization is useful for surgical planning of ductal carcinoma in situ, particularly when considering breast-conserving surgery.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The use of screening mammography (MMG) in the United States has resulted in a significant increase in the rate of detection of ductal carcinoma in situ (DCIS) from 5% to 25–30% (1,2). The introduction of screening MMG will lead to increased detection of asymptomatic and impalpable DCIS in Japan (3). Breast-conserving surgery for DCIS is gaining acceptance (4,5). The main problem with breast-conserving surgery is local recurrence. Price et al. reported that up to 30% of patients develop recurrent disease following breast-conserving surgery for DCIS within 15 years and, of these, about 50% will have invasive cancer (6). Complete excision with clear margins was associated with a lower tumor recurrence rate (7–9). Margin width is an important factor in predicting the risk of local recurrence following breast-conserving surgery (10–14).
MMG will play an important role in the evaluation of DCIS, and also its detection. The assessment of tumor extension obtained by MMG may assist in the selection of patients for breast-conserving surgery and guide the appropriate extent of excision. Holland and co-workers analyzed the association between microcalcification and histopathological tumor extension (15,16), but there is nothing in the literature regarding the association in other MMG subtypes. There are some reports of association in the less common MMG findings of breast malignancy (17,18) and breasts with DCIS (19). The association between subtypes of MMG findings and histopathological tumor extension has remained unclear, particularly in patients with DCIS. In this study, we investigated the relationship between MMG tumor extension and histopathological tumor size according to the MMG subtype. In addition, we compared palpated tumor size with histopathological tumor size according to the MMG subtype in DCIS with palpable tumor.
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PATIENTS AND METHODS |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Between January 1990 and December 1999, 2757 operations for breast cancer, including 150 breasts with DCIS, were performed at the National Cancer Center Hospital, Tokyo, Japan. There were two radical mastectomies, 117 modified radical mastectomies, 10 simple mastectomies, one total glandectomy and 20 involving breast-conserving surgery. The medical records and pathology reports of 130 consecutive series of DCIS that were treated by mastectomy or total glandectomy only were reviewed. The following patients were excluded from this analysis: 14 patients who underwent open biopsy at another hospital, two patients with ipsilateral invasive breast cancer, one patient with minute DCIS discovered incidentally when she had a biopsy for a benign tumor and four patients whose records were not adequate for analysis. The study population included 107 patients with unilateral DCIS and one with bilateral DCIS for a total of 109 breasts with DCIS in 108 patients.
The procedures for histopathological diagnosis before mastectomy included 32 fine-needle aspiration cytologies, seven nipple discharge cytologies, two core needle biopsies, 43 open biopsies and 22 intraoperative open biopsies. Three mastectomies without prior histopathological diagnosis were carried out.
Ninety-three percent of breasts (101 of 109) were symptomatic at referral, 70 had palpable mass, 28 had nipple discharge and three had erosion of nipple. Seven percent of cases (eight of 109) were detected by screening MMG.
The background factors of age, menopausal status, estrogen receptor and predominant histopathological pattern were analyzed. The predominant histopathological pattern of DCIS was categorized as comedo or non-comedo type, including five breasts with intracystic carcinoma.
Mammomat 3 and 3000 (Siemens, Germany) were used for MMG examinations. Mediolateral and craniocaudal MMG views, including spot magnification views, were available for every patient. Radiologists in our hospital evaluated the MMG findings preoperatively, which were categorized as either microcalcification, spiculated, circumscribed or fibrocystic-change type.
The microcalcification type consisted of breasts with apparently malignant clustered microcalcifications, regardless of the presence or absence of tumor shadow. Malignant-appearing microcalcifications were defined as numerous fine, linear or pleomorphic microcalcifications showing a linear or clustered distribution. The spiculated type consisted of breasts with spiculated or ill-defined tumor shadows. The circumscribed type consisted of breasts with circumscribed tumor shadows, suggesting a benign tumor. The fibrocystic-change type consisted of a dense and nodular parenchymal shadow, suggesting fibrocystic disease or no abnormal finding on MMG. Indirect signs, including a single dilated duct or asymmetry of breast tissue, were categorized in the fibrocystic-change type.
The last two subtypes were diagnosed as no malignancy by MMG prior to histopathological examination.
Typical cases of these subtypes are shown in Fig. 1.
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We analyzed the relationship between the MMG and histopathological tumor size by stratifying each category. MMG tumor size was defined as the largest diameter of the tumor measured with sliding calipers and was recorded preoperatively. In cases with microcalcification type, the longest distance between microcalcifications on MMG was used as the MMG tumor size. In fibrocystic-change type cases, MMG tumor size could not be measured and was excluded from this evaluation.
The entire surgical specimens taken by mastectomy were sectioned transversely to 10 mm thickness. Histopathological tumor size was measured under a microscope on the individual cross-section. If open biopsy had been performed before mastectomy, the orientation of the biopsy specimen was reported to the pathologist, the specimen was reconstructed and then the size of lesion was calculated.
In only one breast with distinct multiple tumors was the largest MMG tumor size compared with the largest histopathological tumor size. The discrepancy between MMG tumor size and histopathological tumor size was analyzed according to each MMG subtype.
There were 88 breasts (80.7%) with palpable tumors. In the breasts with palpable tumors, we compared palpated tumor size and histopathological tumor size according to each MMG subtype. Fibrocystic-change type DCIS was included in this evaluation.
The background factor of age was analyzed by the Kruskal–Wallis test. The chi-squared test was used to determine the statistical significance between the background factors of menopausal status, estrogen receptor status and predominant histopathological pattern. The relationship among MMG tumor size, palpated tumor size and histopathological tumor size was analyzed statistically by a paired t-test. The differences in tumor size between histopathology and MMG in terms of background factors were assessed with Student’s t-test. Differences were regarded as statistically significant when the P value was <0.05. Statistical analysis was performed using Statview version 5.0 (SAS Institute, Cary, NC).
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RESULTS |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The clinicopathological background factors classified by MMG subtypes are shown in Table 1. There was no significant difference in terms of age, menopausal status, predominant histopathological pattern and estrogen receptor status in each MMG subtype. In the five breasts with non-invasive intracystic carcinoma, four were categorized as circumscribed type by MMG and one breast was of spiculated type. The predominant histopathological pattern of non-invasive intracystic carcinoma was the non-comedo type.
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MMG tumor size and histopathological tumor size according to MMG subtypes are shown in Table 2. There was no statistical difference between MMG tumor size and histopathological tumor size in microcalcification and spiculated type (microcalcification type, P = 0.60; spiculated type, P = 0.72). MMG tended to overestimate the tumor size in the circumscribed type with marginal significance (P = 0.055).
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The number, palpated and histopathological tumor size in 88 breasts according to MMG subtype are shown in Table 3. In the microcalcification and fibrocystic-change type, histopathological tumor size was significantly larger than palpated tumor size. In the circumscribed type, histopathological tumor size was smaller than palpated tumor size with marginal significance (P = 0.078).
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The length of MMG tumor size minus histopathological tumor size according to MMG subtype in 86 breasts excluding fibrocystic-change type is shown in Fig. 2. Most breasts (about 70%) were estimated with a discrepancy within 20 mm in each subtype. In the circumscribed type, no breast was underestimated more than 20 mm.
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The length of MMG tumor size minus histopathological tumor size according to MMG subtype was compared, with the exception of the fibrocystic-change type, stratified by background factors including age (<50/
50 years) (P = 0.98), menopausal status (premenopausal/postmenopausal) (P = 0.91), predominant histopathological pattern (comedo/non-comedo) (P = 0.59) and estrogen receptor status (positive/negative) (P = 0.91). There was no significant difference among these factors. |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Mammographically detected microcalcifications were observed in 62–98% of DCIS (19–21). In this study, 47.7% of cases were categorized as microcalcification type. The proportion of microcalcification type was smaller than in the literature. The disparity in the proportion of the microcalcification type can be attributed to patient selection, because patients who underwent breast-conserving surgery were excluded from this study and most of our patients (93%) had clinical complaints initially.
Holland et al. reported that MMG estimates of tumor size, based on the extent of microcalcification, frequently underestimated the histopathological tumor size in cases with DCIS (15). However, the data were inconsistent with our results.
The extent of the discrepancy was partly related to the histopathological pattern of DCIS, especially in predominant non-comedo type, associated with fine-granular microcalcification (15,20,22), which tended to be underestimated more than the comedo type (15). Magnification views are useful for detection of fine-granular microcalcifications (16). A discrepancy between MMG and histopathological size <2 cm was seen in 80–85% of cases, irrespective of the histopathological pattern, when a magnified view was applied (16). In the present study, we confirmed this tendency; a discrepancy between MMG and histopathological tumor size within 2 cm was seen in 76.9% of microcalcification type breasts. Since we used a magnified view for every breast in this study, MMG adequately evaluated the tumor size irrespective of histopathological pattern. Computed tomography and/or magnetic resonance imaging precisely describe cancerous extension (23). Using these new diagnostic images, patients with microcalcification type can be candidates for breast-conserving surgery.
With regard to the palpable tumor size, it was significantly smaller than the histopathological tumor size in microcalcification and fibrocystic-change type; only for the spiculated type did palpation appropriately estimate tumor size. We therefore estimated the tumor extension adequately by both MMG and palpation in the spiculated type.
In the circumscribed type, MMG and palpation tended to overestimate the tumor size in the present study. Voogd et al. reported that the proportion of patients with non-circumscribed tumors on MMG who had undergone re-excision after an initial biopsy was significantly higher compared with circumscribed tumors, although this study focused on invasive breast cancer (24). The circumscribed type may have a lower risk of leaving a residual tumor when breast-conserving surgery is performed. Most intracystic carcinomas classified as the circumscribed type may exacerbate the increasing frequency of overestimation by MMG.
In the fibrocystic-change type, we could not estimate the tumor extent accurately by MMG, but all patients had clinical symptoms. The tumor sizes of 16 of 23 breasts (70%) were estimated by palpation. However, the histopathological tumor size was significantly underestimated by palpation only (P = 0.040). One should therefore be careful when performing breast-conserving surgery for the fibrocystic-change type.
In conclusion, MMG categorization is useful for surgical planning of DCIS, particularly when considering breast-conserving surgery.
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FOOTNOTES |
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+ For reprints and all correspondence: Takashi Fukutomi, Breast Surgery Division, National Cancer Center Hospital, 1–1, Tsukiji 5-chome, Chuo-ku, Tokyo 104-0045, Japan. E-mail: tfukutom@gan2.ncc.go.jp
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Received September 5, 2001; accepted February 13, 2002
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