Missed Breast Cancer in Oregon: Mammograms and Discovery Rule

Breast cancer is the second leading cause of cancer death in women, behind only lung cancer. The American Cancer Society puts a U.S. woman's lifetime risk of developing breast cancer at about 13 percent — roughly one in eight.¹ When a tumor that should have been caught at screening is found years later — at a more advanced stage, with fewer treatment options — Oregon families often want to know whether the delay is grounds for a medical-malpractice claim.

This post explains how Oregon law treats missed-mammogram and missed-breast-cancer cases: why mammograms sometimes miss cancer, what the standard of care typically requires when a patient has a palpable lump despite a normal mammogram, how Oregon's discovery rule under ORS 12.110(4) affects the deadline, and what an attorney evaluates when reviewing a delayed-diagnosis claim.

Why mammograms miss cancer

Mammography is an essential screening tool, but it is not perfect. The American Cancer Society states that screening mammograms miss about one in eight breast cancers.² Several factors drive that false-negative rate:

• Dense breast tissue. Glandular and fibrous breast tissue appears white on a mammogram. So does cancer. In women with dense breasts, that overlap reduces sensitivity. ACS notes that women with dense breasts are more likely to get false-negative results.²
• Tumor location. Tumors near the chest wall, deep in the axillary tail, or in the very dense central breast can be missed even on a high-quality study.
• Reading errors. Radiologists are human. A subtle finding — an asymmetry, a developing density, or a small cluster of microcalcifications — can be overlooked in a routine batch of screening reads.
• Image-quality issues. Improper positioning, motion artifact, or technique problems can make a lesion invisible or non-evaluable on a given study.

Understanding that mammography misses cancer is the starting point for the standard-of-care analysis when a patient has clinical symptoms despite an apparently normal screening mammogram.

What standard of care looks like after a "normal" mammogram

When a woman feels a lump and the mammogram comes back normal, the medical question is whether further workup is required. ACS's own guidance on this point is clear: it is important to see a doctor for new breast symptoms even after a recent normal screening mammogram, and additional tests such as a diagnostic mammogram or breast ultrasound may be needed to look more closely at the symptomatic area.²

In a delayed-diagnosis claim, the focus is on whether the clinician acted on those findings. Common patterns include:

• Reassurance without further testing. A patient reports a palpable lump; the screening mammogram is read as normal; no diagnostic mammogram, ultrasound, or biopsy is ordered, and the patient is told to follow up at the next annual screening.
• Failure to act on dense-breast notifications. A radiology report flags dense tissue but no supplemental imaging — diagnostic mammogram, ultrasound, or MRI — is recommended for a symptomatic patient.
• No comparison with prior films. A new asymmetry or developing density is not compared with prior mammograms, which can hide a slowly evolving tumor.
• Delayed biopsy referral. A suspicious finding is graded as "probably benign" with a six-month follow-up, but the next study is not scheduled or performed; the cancer continues to grow during the gap.
• Lost results. The radiology report recommends biopsy or additional imaging, but the recommendation never reaches the patient or the ordering clinician.

Whether any of those patterns falls below the standard of care depends on the specific facts and the testimony of qualified experts — typically a breast-imaging radiologist, a primary-care or OB/GYN expert, and sometimes a breast surgeon.

How a missed breast cancer becomes a malpractice claim

Oregon medical-malpractice claims follow the four-element framework of duty, breach, causation, and damages. In a missed-breast-cancer case, that means proving:

• Breach. A reasonably careful clinician in the same specialty — radiologist, primary-care physician, OB/GYN, or breast surgeon — would have done something different. That might mean ordering a diagnostic mammogram or ultrasound instead of relying on a normal screening study, recommending biopsy of a suspicious finding, or following up on a "probably benign" lesion as required.
• Causation. Earlier diagnosis would more likely than not have changed the outcome — for example, by allowing breast-conserving surgery instead of mastectomy, by avoiding chemotherapy, by preventing distant metastasis, or by improving long-term survival.
• Damages. The patient experienced harm — additional surgery, chemotherapy, radiation, lasting physical effects, or shortened life expectancy — beyond what timely care would have caused.

Oregon law requires expert testimony to establish the standard of care and the breach. A bad outcome alone is not malpractice; the experts must explain what should have happened, what actually happened, and how the difference affected the patient's care.

The discovery rule and the deadline

A patient with a missed breast cancer often does not learn the diagnosis was missed until a new doctor compares old films to a new one, or until a metastasis appears that traces back to an earlier overlooked lesion. Oregon's statute of limitations accounts for that delay through the discovery rule.

Under ORS 12.110(4), a medical-malpractice action must be commenced within two years from the date when the injury is first discovered or in the exercise of reasonable care should have been discovered.³ In missed-breast-cancer cases, discovery usually means the moment the patient is told that the prior mammogram was misread, that a finding was missed, or that the cancer was likely present on an earlier study. The two-year clock generally runs from that date — not from the date of the original mammogram.

ORS 12.110(4) also imposes a five-year statute of repose: with limited exceptions for fraud, deceit, or misleading representation, the action must be filed within five years of the treatment, omission, or operation regardless of when the injury was discovered.³ When the misread happened many years ago, that outer limit can bar an otherwise meritorious claim, even though false-negative mammograms are well known to occur even with appropriate technique.

What an attorney evaluates

When an Oregon attorney reviews a possible missed-breast-cancer claim, the questions are usually:

• Does the prior mammogram, ultrasound, or MRI show a finding the radiologist or primary clinician missed or downgraded?
• Did the patient report symptoms — a palpable lump, nipple change, skin change, or pain — that should have prompted diagnostic imaging or biopsy regardless of the screening result?
• Were dense-breast notifications and follow-up recommendations acted on?
• Did the delay change the staging, treatment options, or prognosis in a way the records and experts can document?
• Are the deadlines under ORS 12.110(4) — both the two-year discovery rule and the five-year outer limit — still open?

These questions are evidence-driven. A delayed breast-cancer diagnosis is sometimes malpractice, sometimes the result of a tumor that was simply not visible on the available imaging, and sometimes a combination of both. Pulling the films, the reports, and the medical record and reviewing them with experienced breast-imaging and oncology experts is the only honest way to answer.

This article is educational

This article describes Oregon law in general terms. It is not legal advice and does not create an attorney-client relationship.

Time limits matter. Most Oregon personal-injury and auto-accident claims must be filed within two years of the injury or accident. Medical malpractice claims must be filed within two years of when you knew or reasonably should have known of the negligence, with an outer limit of five years from the act itself (with a fraud exception). Wrongful death claims must be filed within three years of the date of death. Claims against public bodies (cities, counties, state agencies, public hospitals) require a notice of claim within 180 days. Missing these deadlines typically ends a case.

If you think you may have a claim, call Huegli Law at 971-317-6436 for a free case review. Todd Huegli is licensed in Oregon and consults on cases in Oregon only.

Footnotes

1. American Cancer Society, How Common Is Breast Cancer? https://www.cancer.org/cancer/types/breast-cancer/about/how-common-is-breast-cancer.html ↩

2. American Cancer Society, Limitations of Mammograms. https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/limitations-of-mammograms.html ↩ ↩² ↩³

3. ORS 12.110 — Actions for certain injuries to person not arising on contract. https://oregon.public.law/statutes/ors_12.110 ↩ ↩²