McSweeney v Health Service Executive (Approved)

Factual and Procedural Background

The Plaintiff, a registered nurse with a strong family history of breast cancer, underwent periodic surveillance mammography at The Hospital. She alleges that the Defendant negligently interpreted mammograms from October 2020 and January 2022, failing to recall her for further assessment, which resulted in delayed biopsy and a diagnosis of breast cancer in 2023. The trial proceeded on a modular basis by agreement of the parties; the present module was confined to the issue of breach of duty. The reporting radiologist for the 2020 study was Reporting Radiologist 1; the 2022 and 2023 studies were reported by Reporting Radiologist 2. Expert evidence was led by the Plaintiff's Expert Radiologist and the Defendant's Expert Radiologist concerning the proper interpretation and classification of microcalcifications using the Royal College of Radiologists (RCR) breast imaging classification system.

Legal Issues Presented

1. Whether, applying the RCR breast imaging classification and relevant standards of clinical negligence, it was within the range of acceptable professional judgment to classify the October 2020 mammogram as RCR Category 2 (benign) rather than to recall for further assessment.
2. Whether, applying the RCR classification and relevant standards of clinical negligence, it was within the range of acceptable professional judgment to classify the January 2022 mammogram as RCR Category 2 rather than as RCR Category 3 (indeterminate) thereby requiring recall for further assessment.

Arguments of the Parties

Plaintiff's Arguments

• The October 2020 and January 2022 mammograms showed a new cluster of microcalcifications in the upper anterior left breast whose morphology and distribution were indeterminate and mandated recall for magnification views and biopsy.
• Failure to recall in 2020 and 2022 amounted to a breach of duty leading to delayed diagnosis.

Defendant's Arguments

• The assessments in 2020 and 2022 were properly conducted within established protocols and the RCR classification; the imaging could reasonably be classified as RCR Category 2 given the subtlety, low number, and plausible benign explanations (projection, glandular involution, background microcalcifications).
• The existence of expert disagreement does not itself establish negligence; the Court must assess whether the defendant's approach represented a coherent, rational and professionally recognisable methodology.

Table of Precedents Cited

Court's Reasoning and Analysis

The Court first explained the RCR five-point classification and relevant radiological concepts (microcalcification number, morphology, distribution, cluster definition, effects of projection and glandular involution). It emphasised that RCR Category 2 denotes a very high degree of professional confidence in benignity and that classification between Categories 2 and 3 involves evaluative judgment rather than a mechanical rule. The Court summarised uncontested expert evidence on interpretive difficulty, inter- and intra-observer variability, and the need to avoid hindsight bias.

Applying the established legal principles from Dunne and Morrissey, the Court examined expert disagreement by reference to whether the Defendant's methodology was coherent, rational and professionally recognisable. On the 2020 mammogram the Court found the reporting approach methodical and that the features (a very small number of subtle, arguably amorphous microcalcifications without convincing linear distribution or dominance and with plausible benign explanations such as glandular involution and projection) left the matter within an area of accepted interpretive difficulty in which competent practitioners could differ. Accordingly, classification as RCR Category 2 in 2020 was within the range of acceptable professional judgment.

By contrast, the Court found that by January 2022 the cumulative constellation of features had materially altered the evaluative context: persistence of the focal grouping, increased conspicuity, at least four and possibly five microcalcifications concentrated within a confined area, and partial alignment on the MLO projection. These cumulative features, assessed against the requirement that Category 2 demands a very high level of confidence in benignity, meant that maintaining a Category 2 classification was no longer tenable. The Court concluded that the appropriate classification in January 2022 was at minimum RCR Category 3, requiring recall, and that failure to recall therefore amounted to a breach of duty.

Holding and Implications

Holding: The Court held that classification of the October 2020 mammogram as RCR Category 2 did not constitute a breach of duty, but that classification of the January 2022 mammogram as RCR Category 2 did fall outside the range of acceptable professional judgment and that the Defendant's failure to recall the Plaintiff in January 2022 constituted a breach of duty.

Implications: The direct effect is that the Court found liability in respect of the failure to recall in January 2022 but not in respect of the October 2020 assessment. The opinion applies established standards (Dunne and Morrissey) to the facts and does not purport to create a novel legal rule; it reviews whether the defendant's clinical approach, as applied to the specific factual constellation, remained within professionally acceptable bounds.