Clinical Decision Rule for Palpable Solid Breast Masses
Objective: To develop a clinical decision rule (entitled BREASTAID) that will predict the probability of malignancy in women with palpable solid breast masses.
Summary Background Data: Currently, 80% of open breast biopsies are benign, resulting in excessive economic, psychologic, and physical morbidity.
Methods: A total of 452 solid breast masses were evaluated in a surgical breast clinic between November 1994 and February 1998. Breast cancer status was defined histologically as ductal carcinoma in situ or invasive cancer. Noncancer status included benign histology, mass resolution, or stability at 12-month follow-up. Data were collected on risk factors, clinical breast examination, mammography, and cytology results. Three multiple logistic regression models were used to generate the probability of cancer at 3 logical steps in the workup; Bayes' theorem was applied in a stepwise fashion to generate a final probability of cancer.
Results: A model incorporating only clinical breast examination and mammography resulted in an excessive number of either missed cases or biopsies compared with one that included cytology. Using a cut-point of 4%, this latter BREASTAID model had 97.6% sensitivity and 85.1% specificity. Compared with triple diagnosis, BREASTAID would have reduced the open biopsy rate from 39.8% (180 of 452) to 22.3% (101 of 452), improving the diagnostic yield from 22.7% to 40.6%.
Conclusions: This study convincingly demonstrates that at minimum, clinical, radiologic, and cytologic evaluations are required to accurately evaluate a solid breast mass. BREASTAID has the potential to minimize the number of open biopsies performed while allowing safe triage to follow-up. Before widespread application, further validation studies are required.

In 1970, breast cancer presented as a palpable mass in 90% of patients. Recent reports demonstrate that the majority (55%-68%) of breast cancer cases continue to present with palpable masses, despite the widespread use of screening mammography. While the approach to a solid palpable breast mass is often open surgical biopsy, the malignant/benign breast biopsy ratio in the United States averages only about 1:4, or 20%. Use of this figure and the annual incidence of breast cancer predicts that more than 1 million breast biopsies will be performed in 2002. Using an average reimbursement for open breast biopsy of $2400, the financial cost to the healthcare system in 2002 will be more than $2.4 billion. While many physicians consider open biopsy a minor procedure with few consequences, women pay a significant emotional toll, not only because of the anxiety of the procedure itself but also because of the delay between the clinical evaluation, the operation, and the pathology result. Some women also experience disfigurement as a consequence of the procedure, and subsequent breast cancer screening interpretation can be more difficult because of tissue scarring. Competing with these issues is the acknowledged difficulty of ruling out breast cancer short of open biopsy. In addition, delay in the diagnosis of breast cancer is the most common reason for malpractice litigation in the United States. This reality provides strong incentives for surgeons to continue to perform the procedure, despite its low malignant/benign ratio and associated morbidities.

Triple diagnosis has been used to decrease the open biopsy rate for solid breast masses, a technique that combines the results of clinical impression, mammography, and fine needle aspiration biopsy (FNAB). When all three results are concordant for benign disease, follow-up rather than biopsy is advised. However, triple diagnosis has several limitations. First, the ill-defined interpretive criterion associated with the clinical impression limits its application to experienced examiners. Triple diagnosis often ignores hypocellular FNAB results, rendering the test useless in up to 20% to 30% of cases. Reporting only positive or negative outcomes for the test results in loss of information, since all three components use multiple categories in their interpretation. Triple diagnosis assumes independence of the tests comprising it, but this has not been tested. Finally, the pretest likelihood of disease (as evaluated by risk factor data), is not formally assessed.

Development of a clinical decision rule (CDR) that could overcome the limitations of triple diagnosis has the potential to significantly impact the healthcare of women. A CDR quantifies the contributions that various components of the history, physical examination, and basic laboratory results make toward the diagnosis. The purposes of this study are threefold: 1) to develop a CDR that will accurately predict the probability of malignancy in women with palpable solid breast masses; 2) to develop a CDR that is practical enough to be used by a general surgeon or primary care clinician; and 3) to compare the CDR to our current method of practice, which employs triple diagnosis. Termed BREASTAID (Breast Risk Evaluation And Scoring System To Aid In the Diagnosis of Mammary Masses), this article reports on these goals and the clinical results of the first stages of CDR development.