Ultrasound Can Estimate the Pathologic Size of Infiltrating Ductal Carcinoma FREE

BREAST-CONSERVING surgery has become established as a local treatment equivalent to mastectomy for appropriately selected patients with breast cancer. Removing the malignant tumor with a margin of normal breast tissue can provide equivalent survival when compared with removal of the entire breast.¹ Local therapy has been increasingly directed toward the minimal removal of normal tissue. Reports of minimally invasive cryotherapy² or laser ablation³ of breast tumors have been published. These techniques rely on radiographic imaging to establish the extent of treatment.

Neoadjuvant (preoperative) chemotherapy is often used in advanced breast cancer and is now being investigated in early-stage breast cancer. It has been shown to potentially downstage tumor size and stage prior to surgery, allowing breast conservation in some women who would have otherwise required mastectomy.⁴ Preoperative staging in these neoadjuvant trials is done clinically, relying on physical examination and/or imaging studies to assess initial tumor size. Ultrasound (US) is often the imaging tool used to estimate the in situ dimensions of a malignant tumor.

This study was conducted to determine whether US correlates with tumor size as measured by pathologic examination in providing accurate tumor staging.

A retrospective medical record review of all women diagnosed with breast cancer at the University of Colorado Breast Center, Denver, between January 1, 1994, and July 1, 1997, was conducted. Forty-five women were identified who had breast US as part of their diagnostic evaluation. Eleven patients were excluded from the study. The reasons for exclusion were tumor not identifiable on US (4 patients), US performed on a synchronous benign lesion and not on the malignant lesion (2 patients), inflammatory breast cancer treated with neoadjuvant therapy (1 patient), refusal of surgery or surgery done elsewhere (3 patients), and medical records not available for evaluation (1 patient). Thirty-five tumors were evaluated. Statistical analysis was performed with the StatView software (Abacus Concept Inc, Berkeley, Calif) using the paired t test. In most cases, pathologic size was measured on fresh tissue.

Tumor histology included 30 with invasive ductal carcinoma with and without associated ductal carcinoma in situ, 2 pure ductal carcinoma in situ, 1 lobular carcinoma, 1 medullary carcinoma, and 1 tubular carcinoma. When all tumors are included in the study, the tumor size as measured by US ranged from 0.45 cm to 3.81 cm. The tumor size when measured by pathologic examination ranged from 0.5 cm to 5 cm. The mean tumor size difference when measured by US vs pathologic size was 0.4 cm (P = .01). The range of tumor size difference was −1.6 cm to +1.2 cm. Not surprisingly, the most significant underestimation in tumor size was the 1 tumor of lobular histology. The US-measured size was 1.5 cm, whereas the pathologic size was 5 cm.

If only tumors with invasive ductal histology are evaluated, the mean difference in size is 0.33 cm (P = .008). The range of difference was −1.6 cm (US size smaller than pathologic size) to 0.42 cm (US size larger than pathologic size). Although 56% of the invasive ductal tumors were underestimated by US, only 17% were underestimated by more than 1 cm; no tumor was underestimated by more than 2 cm (Table 1).

The ability to determine pathologic size in situ is important for appropriate treatment planning. When surgical staging is not done initially, other forms of clinical staging must be used. Other forms of imaging that have been investigated for the ability to provide accurate in situ tumor staging are mammography, computed tomography, magnetic resonance imaging, and US. Yang et al⁵ compared US, magnetic resonance imaging, and mammography with pathologic size in 39 patients. They concluded that US had the most value of these imaging modalities in staging breast cancer.

This study confirms these conclusions. Although US tends to underestimate the pathologic tumor size, 83% of invasive ductal tumors fall within a 1-cm and 100% fall within a 2-cm extension of the US-measured tumor size. Therefore, in invasive ductal carcinoma, US can be used to approximate tumor size and monitor the extent of the treatment area when developing very localized therapeutic tools.

These data were presented as a poster at the San Antonio Breast Conference, San Antonio, Tex, December 12, 1998.

Dr Finlayson wishes to acknowledge the support of the University of Colorado Cancer Center, Denver.

Corresponding author: Christina A. Finlayson, MD, Department of Surgery, University of Colorado Health Sciences Center, 4200 E Ninth Ave, Box C-311, Denver, CO 80262 (e-mail: christina.finlayson@uchsc.edu).