Breast Cancer Method of Detection: Frequently Asked Questions

The initial method of detection (MOD) refers to the first imaging examination, physical symptom, or clinical sign that prompts further investigation and ultimately leads to a new breast cancer diagnosis. The MOD is assigned at the patient level and falls into 1 of 3 categories: screening in asymptomatic patients, detection by patients or health care providers, or neither of the above. The MOD should be assigned prospectively by the radiologist when interpreting an examination with a final BI-RADS category of 4 or 5, before image-guided biopsy and breast cancer diagnosis. The MOD is not assigned to examinations classified as BI-RADS category 0, 1, 2, 3, or 6, nor is it assigned in the setting of an active breast cancer diagnosis. This Clinical Practice article addresses frequently asked questions and challenging clinical scenarios compiled by the American College of Radiology's Screening and Emerging Technology Committee to guide consistent MOD assignment. For example, if a patient presents with a lump but is ultimately found to have a suspicious finding requiring biopsy in the contralateral breast, the MOD should reflect the reason for presentation, the patient-detected symptom (Pat), even if the cancer itself is asymptomatic. By increasing awareness of MOD and standardizing MOD reporting practices, radiologists can contribute to improved data collection. While MOD is not currently tracked in U.S. cancer registries, its systematic collection may offer valuable insights into screening effectiveness, technology performance, and disparities in cancer detection. Standardized MOD reporting has the potential to strengthen early detection efforts and improve outcomes across diverse clinical settings.