The visibility of cancer on previous mammograms in retrospective review

AIM: To study how many tumours were visible in restrospect on mammograms or iginally reported as normal or benign in patients coming to surgery with pr oven breast cancer. The effect of making the pre-operative mammogram availa ble was also assessed. MATERIALS AND METHODS: Three hundred and twenty initial mammograms of conse cutive new breast cancer cases were analysed by a group of radiologists in the knowledge that all patients were later diagnosed with breast cancer. Th e films were read twice, first without and then with the later (pre-operati ve) mammograms available. The parenchymal density in the location of the tu mour was classified as fatty, mixed or dense, and the tumours were classifi ed as visible or not visible, The reasons for the invisibility of the tumou r in the earlier examination were analysed. RESULTS: Fourteen per cent (45) of cancers were retrospectively visible in earlier mammograms without the pre-operative mammograms having been shown, and 29% (95) when pre-operative mammograms were shown. Breast parenchymal d ensity decreased with age and the visibility of tumours increased with age. When considered simultaneously, the effect of age (over 55 vs under 55) wa s greater (OR = 2.9) than the effect of density (fatty vs others) (OR = 1.5 ). The most common reasons for non-detection were that the lesion was overl ooked (55%), diagnosed as benign (33%) or was visible only in one projectio n (26%). Growing density was the most common (37%) feature of those lesions originally overlooked or regarded as benign. CONCLUSIONS: Tumours are commonly visible in retrospect, but few of them ex hibit specific signs of cancer, and are recognized only if they grow or oth erwise change, It is not possible to differentiate most of them from normal parenchymal densities. Saaremaa, I. (2001). Clinical Radiology 56, 40-43. (C) 2001 The Royal College of Radiologists.