Investigation of lesions detected by mammography. The Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer. Canadian Association of Radiation Oncologists.

OBJECTIVE: To provide information and recommendations to facilitate decision-making when a mammographic abnormality is detected by screening. EVIDENCE: References identified by use of MEDLINE, AIDSLINE, CANCERLIT and reference lists of review articles to December 1996. Where experimental evidence is lacking, recommendations are based on expert opinion. The evidence is graded accordingly in "levels" (page S2). BENEFITS: Exclusion or confirmation of the presence of cancer with minimum intervention and delay. RECOMMENDATIONS: When an abnormality is detected on screening mammography, clinical evaluation and thorough radiologic work-up are needed to determine its significance. Clinical evaluation should include a history and a thorough examination of the breast, axilla and supraclavicular areas. In the radiologic work-up, diagnostic mammograms should be obtained with additional views, spot compression and magnification views as appropriate. Current mammograms should be compared with previous mammograms whenever possible. The mammographic report should include a precise description of the abnormal features visualized and an estimate of the level of suspicion of cancer they imply. Whenever there is any doubt in the interpretation of mammograms, the interpretation of 2 experienced readers should be obtained. (The following radiologic classification into 4 categories is suggested: 1--benign, not due to cancer; 2--low risk, probability of cancer under 2%; 3--intermediate risk, probability of cancer 2% to 10%; 4--high risk, probability of cancer over 10%.) Ultrasonography can be used to clarify the nature of noncalcified nodular lesions. Management decisions require close communication between the woman and her physicians. Throughout, a clinician in charge should be identified who will coordinate and transmit all decisions. Management will depend on the estimated level of risk Category 1 abnormalities require no further investigation. Category 2 abnormalities may be followed up by periodic mammographic and clinical examinations. Follow-up examination of category 2 abnormalities should be carried out at approximately 6 and 12 months. If the abnormality is stable, examination should be repeated annually for 2 to 3 years thereafter. The rationale of follow-up should be explained, and women should be made aware that it is not possible to provide complete assurance that an abnormality is benign. Category 3 abnormalities usually require image-guided fine-needle or core biopsy. Every image-guided needle biopsy should be accompanied by a full report. Category 4 abnormalities should usually be excised. This may be preceded by image-guided needle biopsy. When surgical biopsy is carried out, the margins of the resected specimen must be free of tumour. The intact pathology specimen should be examined radiographically to confirm that all mammographic abnormalities have been removed. The patient should be kept fully informed as to the reason for each test and the meaning of its results. The process, from initial detection of the mammographic abnormality to the final management decision, should be completed as rapidly as possible. VALIDATION: Guidelines were reviewed and revised by the Writing Committee, expert primary reviewers, secondary reviewers selected from all regions of Canada and by the Steering Committee. The final document reflects a consensus of all these contributors.