2 - INVESTIGATION OF LESIONS DETECTED BY MAMMOGRAPHY

Objective: To provide information and recommendations to facilitate de cision-making when a mammographic abnormality is detected by screening . Evidence: References identified by use of MEDLINE, AIDSLINE, CANCERL IT and reference lists of review articles to December 1996. Where expe rimental evidence is lacking, recommendations are based on expert opin ion. The evidence is graded accordingly in ''levels'' (page S2). Benef its: Exclusion or confirmation of the presence of cancer with minimum intervention and delay. Recommendations: When an abnormality is detect ed on screening mammography, clinical evaluation and thorough radiolog ic work-up are needed to determine its significance. Clinical evaluati on should include a history and a thorough examination of the breast, axilla and supraclavicular areas. In the radiologic work-up, diagnosti c mammograms should be obtained with additional views, spot compressio n 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 im ply. Whenever there is any doubt in the interpretation of mammograms, the interpretation of 2 experienced readers should be obtained. (The f ollowing 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 r isk, probability of cancer over 10%.) Ultrasonography can be used to c larify the nature of noncalcified nodular lesions. Management decision s require close communication between the woman and her physicians; Th roughout, a clinician in charge should be identified who will coordina te and transmit all decisions. Management will depend on the estimated level of risk Category 1 abnormalities require no further investigati on. Category 2 abnormalities may be followed up by periodic mammograph ic and clinical examinations. Follow-up examination of category 2 abno rmalities should be carried out at approximately 6 and 12 months. If t he abnormality is stable, examination should be repeated annually for 2 to 3 years thereafter. The rationale of follow-up should be explaine d, and women should be made aware that it is not possible to provide c omplete assurance that an abnormality is benign. Category 3 abnormalit ies usually require image-guided fine-needle or core biopsy. Every ima ge-guided needle biopsy should be accompanied by a full report. Catego ry 4 abnormalities should usually be excised. This may be preceded by image-guided needle biopsy. When surgical biopsy is carried out, the m argins of the resected specimen must be free of tumour. The intact pat hology specimen should be examined radiographically to confirm that al l 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 a bnormality to the final management decision, should be completed as ra pidly as possible. Validation: The guidelines were reviewed and revise d by a writing committee, expert primary reviewers, secondary reviewer s selected from all regions of Canada and by the Steering Committee. T he final guidelines reflect a consensus of all these contributors.