Mammogram Misinterpretation Claims

What “mammogram misinterpretation” usually means

It is important to understand that radiology,the reading of medical images,is a human skill involving complex judgement, not an automated computer process. While technology has improved, the experience and vigilance of the consultant radiologist remain central to an accurate diagnosis. A "misinterpretation" generally refers to a situation where a reasonably competent radiologist should have identified an abnormality that was missed or dismissed.

Missed finding

This occurs when an abnormality is clearly visible on the mammogram image but is simply not seen or reported by the radiologist. In retrospect, when the images are reviewed by independent experts, the signs of disease are evident, yet the original report declared the scan normal. This is often referred to as a perceptual error.

Mischaracterised finding

In this scenario, the radiologist identifies an area of concern but interprets it incorrectly. They may decide that a shadow or density is benign (harmless) without ordering necessary further tests, such as an ultrasound or biopsy, to confirm their opinion. If that area later proves to be malignant (cancerous), the initial decision to dismiss it without triple assessment may be considered a breach of duty.

Reporting or communication breakdown

Sometimes the error is not in the reading of the image, but in what happens next. Common issues include:

• Findings noted but not acted upon: The report mentions a density but does not explicitly recommend a biopsy or follow-up.
• Unclear instructions: The report uses vague language that does not convey the urgency to the referring GP or surgeon.

Technical limitations vs avoidable error

Not every delayed diagnosis is due to negligence. Sometimes, a mammogram is technically difficult to read due to the positioning of the breast or the density of the tissue.

• Technical limitations: If the cancer was hidden behind dense tissue and genuinely could not be seen, this is often considered a limitation of the technology, not negligence.
• Avoidable error: If the scan quality was poor (e.g., blurred or incomplete) and the radiologist accepted it rather than asking for a repeat scan, this may be considered a failure in the standard of care.

How mammograms are read and reported

To understand where errors happen, it is helpful to understand the reading process itself.

The reading process in practice

A consultant radiologist reviews your images on high-resolution monitors. They look for specific indicators of cancer, such as masses, architectural distortion (twisting of the tissue), or clusters of microcalcifications (small calcium deposits). The report they produce is the formal record of their findings and, crucially, their recommendations for the next steps.

Double reading and arbitration

In the national screening programme (BreastCheck), every mammogram is read by two separate readers.

• If both agree the scan is normal, you receive a clear result.
• If both agree it is abnormal, you are recalled for assessment.
• Arbitration: If the two readers disagree, the case is sent to a third senior radiologist or a consensus meeting to decide the outcome. Errors can sometimes occur here if a correct "suspicious" opinion is overruled by the arbitration process.

Classification language patients may see

Radiologists often use a grading system to describe how suspicious a finding is. While different hospitals may use slightly different codes, they generally follow a scale like the "R" or "M" scale:

• R1 / M1: Normal.
• R2 / M2: Benign (harmless).
• R3 / M3: Indeterminate/Equivocal (unsure, requires biopsy).
• R4 / M4: Suspicious of malignancy.
• R5 / M5: Highly suspicious of malignancy.

A misinterpretation claim often involves a lesion that should have been graded R3 or higher (requiring biopsy) being graded as R1 or R2 (discharge).

Correlation with clinical findings

Radiology cannot be viewed in isolation. If a patient feels a lump, the radiologist must ensure the mammogram covers that specific area. If the mammogram looks clear but the lump is palpable, the radiologist has a duty to advise further investigation (usually ultrasound) rather than simply reporting "normal mammogram."

Common mammogram interpretation problems

In our experience assisting clients with these enquiries, certain types of interpretation errors appear frequently.

Failure to compare with prior imaging

One of the most powerful tools a radiologist has is your previous history. A small density might look unremarkable on its own, but if it was not there two years ago, it represents a change. Failure to retrieve and compare old films is a common source of missed diagnoses.

Dense breast tissue and subtle findings

Breast density refers to the amount of fibrous and glandular tissue compared to fatty tissue. On a mammogram, fat looks dark, while cancer and glandular tissue both look white. In dense breasts, cancer can be hidden. While density makes reading harder, radiologists must be extra vigilant. If the view is obscured, they should often proceed to ultrasound rather than declaring the breast "clear."

Subtle distortion or asymmetry

Not all breast cancers present as a distinct "lump." Some invasive cancers present as architectural distortion,a subtle pulling or twisting of the breast tissue. These signs are easily missed by a rushed or inexperienced reader but are classic indicators that a reasonably competent radiologist should spot.

Technical quality issues

A report relies on a good picture. Errors occur when:

• Poor positioning: The breast tissue was not pulled forward enough, leaving the cancer off the edge of the picture.
• Motion blur: The patient moved slightly, making fine details impossible to see.
• Incomplete views: The radiologist accepted a substandard image instead of recalling the patient for a retake.

Post-surgical or complex cases

If a patient has had previous breast surgery or has implants, the resulting scar tissue can mimic or hide cancer. Interpreting these scans requires a higher level of expertise to distinguish between a safe post-operative scar and a new recurrence.

Misinterpretation of calcifications

Microcalcifications are tiny white specks on the scan. While many are benign, certain patterns (clustered, linear, or branching) are early signs of DCIS (Ductal Carcinoma in Situ). Dismissing these as benign without a closer magnification view or biopsy is a frequent area of dispute.

Where the system can fail even when the image is reported

Sometimes, the radiologist spots the issue, but the safety net fails. These are administrative or systems failures that are equally damaging.

• Failure to recall or expedite assessment: A report may be marked "abnormal," but due to clerical error, the recall letter is never sent, or the appointment is not scheduled. This is a failure of the hospital's administration system.
• Missed follow-up on recommended ultrasound or biopsy: The radiologist might write, "Mammogram equivocal, recommend ultrasound." If this recommendation is overlooked by the referring doctor or the clinic staff, the patient is sent home with false reassurance.
• Result communication gaps: We have seen cases where:
  • Letters are sent to the wrong address.
  • GPs are not copied on the results.
  • Patients are told verbally "everything is fine" by a staff member who misread the file, despite a formal report suggesting otherwise.
• Addendum or amended report not communicated: Occasionally, a radiologist may review a scan later (e.g., at a multidisciplinary meeting) and issue an addendum changing the result from benign to suspicious. If this crucial update is not communicated to the patient or their GP immediately, treatment is delayed.

Diagnostic assessment and the “triple assessment” pathway

The Triple Assessment is the gold standard for diagnosing breast problems. It consists of:

1. Clinical examination (doctor feeling the breast).
2. Imaging (Mammogram and/or Ultrasound).
3. Pathology (Biopsy/sample of cells).

Errors often occur when this protocol is not completed.

Mammogram plus targeted ultrasound

Mammograms are excellent for seeing calcifications and distortions, while ultrasounds are better at telling solid lumps from fluid-filled cysts. In symptomatic patients, relying on a mammogram alone is rarely sufficient. If a lump is felt, an ultrasound is almost always required, even if the mammogram looks normal.

Biopsy decision-making

The rule of thumb in breast diagnostics is: if in doubt, biopsy. If there is a discordant finding (e.g., the scan looks okay, but the doctor feels a hard lump), a biopsy should be performed to be certain. Failing to take a tissue sample in the presence of persistent symptoms can be negligent.

Imaging-pathology mismatch

After a biopsy, the team must ask: "Does the microscope result match the picture?"

If the mammogram showed a highly suspicious spiky mass, but the biopsy says "normal breast tissue," the team should suspect the biopsy missed the target. Accepting a benign result that doesn't fit the imaging is a critical error known as discordance.

Multidisciplinary review (MDT)

Complex cases should be discussed at an MDT meeting involving surgeons, radiologists, and pathologists. This safety mechanism is designed to catch errors. If a difficult case was not brought to the MDT, and a diagnosis was missed as a result, this may be relevant to a legal claim.

Interval cancers and “clear scan” reassurance

It is important to distinguish between a missed cancer and an interval cancer.

An interval cancer is a cancer that is diagnosed in the period between regularly scheduled screening mammograms. For example, a woman has a clear screen in 2023 and develops a lump in 2024.

Some cancers are biologically aggressive and grow very fast. It is possible for a woman to have a genuinely clear mammogram, and for a new, fast-growing cancer to appear six months later. In these cases, the radiologist did nothing wrong; the cancer simply wasn't there (or wasn't visible) at the time of the scan.

However, if a woman is diagnosed with a large, advanced tumour shortly after a "clear" mammogram, it raises the question: was it visible on the earlier scan? If a retrospective review shows the cancer was present and identifiable at the time of the screen, it may be classified as a missed diagnosis rather than a true interval cancer.

Practical steps if you are concerned a mammogram was misread

If you have been diagnosed with breast cancer and suspect a delay occurred due to prior imaging errors, there are practical steps to take.

• Prioritise medical review: Your health is the priority. Ensure your current treatment plan is fully established. Legal enquiries can be made in the background without disrupting your medical care.
• Records checklist: To investigate a potential claim, a solicitor will eventually need to gather your full file. It is helpful to be aware of what this includes:
  • Mammogram reports: The written interpretation of every scan.
  • Ultrasound reports: Corresponding scan notes.
  • Biopsy results: Pathology reports.
  • Clinic letters: Correspondence between the breast clinic and your GP.
• Timeline building: Try to write down a simple timeline of events while your memory is fresh. Include:
  • Dates you noticed symptoms.
  • Dates of GP visits and what was said.
  • Dates of mammograms and the results you were given.
  • The date of your eventual diagnosis.

How concerns are assessed in Irish medical negligence cases

Investigating these cases requires a strictly forensic approach to establish whether the care provided fell below the legal standard.

Standard of care

In Irish law, a radiologist is not expected to be perfect. They are expected to demonstrate the skill of a "reasonably competent radiologist" acting with ordinary care. The test is not whether a mistake was made, but whether the error was one that no competent radiologist would have made in the same circumstances.

Causation

Proving negligence is only the first step. We must also prove causation. This means showing that the delay actually altered the outcome. We ask:

• Did the cancer grow significantly during the delay?
• Did the staging increase (e.g., spreading to lymph nodes)?
• Did the delay necessitate more aggressive treatment (e.g., mastectomy instead of lumpectomy, or chemotherapy that might otherwise have been avoided)?

Independent expert review

To answer these questions, Michael Boylan LLP engages independent radiology experts from outside the jurisdiction (often from the UK). These experts review the images "blind" (without knowing where the cancer is) to see if they identify the abnormality. If they spot it immediately, it strengthens the case that the original failure was negligent.

Time limits and the “date of knowledge” concept in Ireland

Strict time limits apply to medical negligence cases in Ireland, usually two years. However, in cancer misdiagnosis cases, the start date for this clock can be complex.

The two-year limit does not necessarily start on the date the mammogram was taken. It typically starts from the "date of knowledge",the date you first realised (or should have realised) that an injury had occurred due to a potential error. This is often the date you were finally diagnosed and told that the cancer had been present for some time.

Despite the "date of knowledge" rule, it is always safer to act immediately. Memories fade, staff move on, and systems change. Instructing a solicitor early ensures that your medical records and images are preserved and secured promptly.

FAQs

Can mammograms miss cancers even when care is appropriate?

Yes. Mammography is not 100% sensitive. Approximately 10,15% of breast cancers may not be visible on a mammogram, particularly in women with very dense breast tissue or lobular cancers that do not form a distinct lump. If the cancer was genuinely invisible, the "miss" is not considered negligence.

If symptoms persisted after a “clear” mammogram, what should usually happen next?

If you have a palpable lump or focal pain, a "clear" mammogram is not enough to rule out cancer. The standard of care usually requires further investigation, such as an ultrasound and a clinical examination by a specialist. If you were discharged solely based on the mammogram while symptoms persisted, this may be a failure in care.

What documents are most important to request first?

While your solicitor will request the full file, the most critical items are the radiology images (discs) and the radiology reports from the dates in question, along with the subsequent histology (biopsy) report that confirmed the cancer.

What if a later clinician says an abnormality was visible on an earlier scan?

If a doctor mentions that your cancer is visible on an old scan (a "retrospective review"), write down exactly what they said and when. This is significant information that warrants legal investigation.

How long do I have to seek legal advice in Ireland?

Generally, the Statute of Limitations is two years from the date you knew (or ought to have known) of the negligence. However, given the complexity of determining that date, it is strongly advised to seek legal counsel as soon as you have a concern.

Why Michael Boylan LLP?

At Michael Boylan LLP, we specialise in medical negligence and catastrophic injury law. This specialisation is vital in mammogram misinterpretation cases, which require a deep understanding of radiology protocols, oncology staging, and the specific Triple Assessment guidelines used in Irish hospitals.

We approach every enquiry with empathy and rigour. We understand that you are likely undergoing treatment or recovering from a significant trauma. Our goal is to investigate your concerns thoroughly, providing you with honest, expert answers about whether your care met the required standard, and ensuring you have the support needed to secure your future.

Would you like to discuss your experience?

If you are concerned that a mammogram was misread or that a diagnosis was unreasonably delayed, please contact our team for a confidential discussion. We can help you understand your position and the options available to you.

Contact Michael Boylan LLP today.

*In contentious business, a solicitor may not calculate fees or other charges as a percentage or proportion of any award or settlement.