A mammogram is an X-ray of the breast, but not all mammograms serve the same clinical purpose. Screening mammograms are routine exams for patients with no symptoms. Diagnostic mammograms are ordered when a symptom is present or a screening result requires closer review.
What Is a Screening Mammogram?
A screening mammogram is a routine breast X-ray ordered for patients who have no breast symptoms. The Canadian Cancer Society’s mammography overview describes screening mammography as a tool that monitors breast changes over time and can find cancer at an early stage, before it can be felt. Standard screening takes two images of each breast: one from top to bottom and one from side to side.
The Ontario Breast Screening Program (OBSP) enables women ages 40 to 74 to self-refer for OHIP-covered screening mammograms. Women outside that range or with elevated risk factors may be referred for screening through their primary healthcare provider. Screening results are typically mailed or communicated through your physician after the radiologist has reviewed the images.
What Is a Diagnostic Mammogram?
A diagnostic mammogram is ordered when a patient reports a symptom or when a screening result needs further evaluation. The Canadian Cancer Society notes that diagnostic mammography is done to investigate a breast problem that has been found, such as a lump, nipple discharge, or skin changes. Unlike screening, the radiologist may review the images while the patient is still present, and additional views can be taken on the same visit if needed.
Diagnostic mammograms use more targeted imaging techniques. Spot compression focuses on a specific area of the breast to spread tissue and sharpen the image. Magnification views enlarge an area to assess calcifications or subtle changes in detail.
Screening Mammogram vs. Diagnostic Mammogram: Key Differences
Here’s a simple way to understand the difference between a diagnostic mammogram and a screening mammogram. Both use the same imaging technology, but they are done for different reasons. A screening mammogram is a routine check for patients with no symptoms, while a diagnostic mammogram takes a closer look when there is a specific concern, symptom, or abnormal result that needs further evaluation.
Who Each Exam Is For
Screening is for asymptomatic patients as part of a regular prevention schedule. Diagnostic is for patients who have a symptom, a palpable finding, or an abnormal screening result. Your physician or the screening program determines which exam is appropriate based on your clinical profile.
Appointment Duration and Result Timing
Screening appointments are typically completed in 15 to 20 minutes. Diagnostic appointments take longer because additional views may be requested on the spot. Diagnostic results are frequently communicated the same day; screening results go through a review queue and are sent to your physician after the appointment.
When Each Type of Mammogram Is Used
Physicians use specific clinical criteria to determine which exam is appropriate for each patient.
- Screening is ordered: For asymptomatic women at standard or elevated risk on a routine schedule, typically every one to two years.
- Diagnostic is ordered: When a patient reports a new lump, focal pain, nipple discharge, skin thickening, or breast asymmetry.
- Diagnostic follows abnormal screening: When a screening result is flagged as incomplete or requires further assessment before a final interpretation can be made.
- Diagnostic with implants: Patients with breast implants may require a diagnostic protocol to accommodate additional imaging views.
How Results Are Interpreted
Both exam types use the Breast Imaging Reporting and Data System (BI-RADS) to communicate findings. The BI-RADS scale runs from 0 (incomplete, additional imaging needed) to 6 (known malignancy). A BI-RADS 0 result after screening is what triggers a follow-up diagnostic appointment.
Diagnostic mammogram reports are reviewed by a radiologist and sent to your referring healthcare provider. The Canadian Partnership Against Cancer notes that in most Canadian jurisdictions, patients are notified of abnormal screening results by phone or mail, with follow-up imaging arranged through the screening program or referring physician. Your physician reviews the final report with you and advises on next steps.
Follow-Up Imaging and Next Steps
A diagnostic mammogram result does not always lead to further testing. If the finding is consistent with benign tissue, no further imaging is needed. If the result remains inconclusive or suspicious, follow-up may include breast ultrasound, breast MRI, or biopsy.
- BI-RADS 1 or 2: Negative or benign finding; return to routine screening schedule.
- BI-RADS 3: Probably benign; short-interval follow-up imaging recommended, typically in 6 months.
- BI-RADS 4 or 5: Suspicious or highly suspicious; biopsy is typically recommended.
- BI-RADS 6: Known malignancy; imaging used to guide treatment planning.
Is a diagnostic mammogram more accurate than a screening mammogram?
A diagnostic mammogram is not more accurate in the sense of detecting cancer overall. It is more detailed because it uses additional imaging techniques focused on a specific area of concern. The two exams serve different clinical purposes and are not substitutes for one another.
Do I need a referral for a diagnostic mammogram in Ontario?
Yes. A signed requisition from a licensed Ontario healthcare provider is required. If you were called back after a screening result, the OBSP or your physician will arrange the diagnostic referral. If you have a new symptom, contact your family doctor or a walk-in clinic to obtain a requisition.
Can a diagnostic mammogram replace a screening mammogram?
No. A diagnostic mammogram investigates a known concern; it does not replace routine screening. Once a diagnostic workup is complete and findings are resolved, patients return to their standard screening schedule. Both exams are part of a breast health pathway, not alternatives to each other.
What the Right Exam Means for Your Breast Imaging Pathway?
Screening and diagnostic mammograms each serve a defined role in the breast imaging pathway. Screening detects early changes in asymptomatic patients; diagnostic clarifies findings that require a closer look. Your referring provider determines which exam is appropriate based on your symptoms, screening history, and risk profile.
For more information, visit www.welldiagnostics.ca/mammography-obsp
