Increased-Risk Causation: An Oncologist’s Failure to Question a Conflicting Diagnosis May Require Jury Review

1. Introduction

The Supreme Court of Pennsylvania reaffirmed that uncertainty about whether proper medical treatment would have prevented a patient’s death does not necessarily prevent a malpractice claim from reaching a jury. When expert testimony establishes, to a reasonable degree of medical certainty, that negligent care increased the risk of the harm actually suffered, the jury must decide whether that negligence substantially contributed to the harm.

The case concerned Tanya Smith, whose rare and aggressive lymphoma was initially misidentified as metastatic breast cancer. Her treating oncologist, Annie Kannarkatt, M.D., allegedly failed to question that diagnosis despite subsequent clinical and imaging findings that did not fit it. Smith consequently received approximately thirteen months of inappropriate treatment before the correct diagnosis was made.

The defendants—Dr. Kannarkatt and Cancer Care Associates of York, Inc.—argued that the plaintiffs had not connected the oncologist’s failure to communicate with pathology to Smith’s eventual death. They emphasized the original pathologist’s error, the disease’s poor prognosis, and the causation expert’s inability to predict how Smith would have responded to earlier treatment.

The Court rejected those arguments as grounds for terminating the case before a jury could decide it. Its decision does not create a new cause of action or replace the existing causation framework. Rather, it gives a significant application of the increased-risk-of-harm doctrine established in Hamil v. Bashline, 392 A.2d 1280 (Pa. 1978), to diagnostic failures involving multiple medical providers.

2. Background and Procedural History

The mistaken diagnosis and delayed treatment

In March 2017, Smith underwent a biopsy of an enlarged axillary lymph node. Pathologist John Wright, M.D., described the tissue as metastatic adenocarcinoma compatible with a breast origin. Subsequent CT and PET scans, a mammogram, and an ultrasound did not identify a primary breast tumor; the CT and PET findings also included lymphoma as a possible diagnosis.

Dr. Kannarkatt possessed this additional information when she began treating Smith. Nevertheless, she proceeded with breast-cancer-directed chemotherapy and radiation without seeking further pathological investigation. Although radiation improved the treated areas, chemotherapy produced little or no improvement, and the disease spread substantially.

A biopsy associated with Smith’s gallbladder removal in March 2018 established that she had ALK positive large B-cell lymphoma. Reexamination of the original tissue showed the same disease had been present from the beginning. Smith then received lymphoma-directed treatment at the Milton S. Hershey Medical Center. Salvage chemotherapy reduced the cancer sufficiently to permit a stem cell transplant, but the transplant did not produce a lasting successful outcome. She died on January 6, 2019.

The malpractice allegations

Smith and her husband alleged that Dr. Kannarkatt negligently failed to verify the breast cancer diagnosis, consult pathology about competing findings, and provide appropriate chemotherapy. They claimed that these failures increased the risk of harm, contributed to Smith’s injuries and death, and deprived her of a longer life. Their claims included medical expenses and pain and suffering. Cancer Care Associates faced a claim of vicarious liability.

The litigation

The first trial ended in a hung jury. During the second trial, the trial court entered a compulsory nonsuit after the plaintiffs rested, concluding that their causation evidence was insufficient. It subsequently refused to remove the nonsuit.

The Superior Court vacated the judgment and ordered a new trial. It held that the plaintiffs’ evidence satisfied the increased-risk threshold and that a jury should decide whether Dr. Kannarkatt’s conduct was a substantial factor in Smith’s harm. The Supreme Court granted review of whether the Superior Court had properly applied that causation standard.

3. Summary of the Opinion

The Supreme Court affirmed the Superior Court. Its central conclusions were:

• The expert evidence was sufficient: Viewed favorably to the plaintiffs, it supported a finding that Dr. Kannarkatt’s failure to question an inconsistent diagnosis contributed to delayed appropriate treatment and increased Smith’s risk of disease progression and premature death.
• A certain alternative outcome was unnecessary: The plaintiffs did not have to establish precisely how long Smith would have lived with timely treatment or prove with certainty that contacting pathology would have changed her course.
• The original diagnostic error was not necessarily exclusive: Dr. Wright’s mistake did not foreclose a finding that Dr. Kannarkatt’s subsequent conduct was also a substantial factor.
• The jury retained the ultimate decision: Meeting the evidentiary threshold did not establish liability. Credibility, competing medical explanations, and substantial-factor causation remained for the jury.

The practical result was a new trial, not a judgment awarding damages to the plaintiffs.

4. Precedents Cited and Their Influence

Hamil v. Bashline, 392 A.2d 1280 (Pa. 1978)

Hamil v. Bashline supplied the controlling doctrine. It adopted Section 323(a) of the Restatement (Second) of Torts for circumstances in which a defendant undertakes protective services but negligently increases the risk of harm from an independent source.

The distinction is important: a physician need not have caused the underlying disease to incur liability for negligently failing to protect the patient against its consequences. Here, the independent source of danger was Smith’s cancer; the alleged negligence impaired the opportunity to treat it effectively.

Under Hamil v. Bashline, expert testimony that negligence increased the risk of the harm actually sustained permits the fact-finder to determine whether the increased risk was a substantial factor in producing that harm. The decision relaxes the necessary causal showing without eliminating the requirement of expert medical certainty concerning the increase in risk.

The present Court also relied on that precedent’s policy rationale. A negligent provider should not become immune merely because the consequences of omitted treatment cannot be reconstructed with certainty. Requiring definite proof of the consultation, diagnosis, treatment, and survival that would have occurred could make the uncertainty created by the alleged negligence a complete defense.

Jones v. Montefiore Hosp., 431 A.2d 920 (Pa. 1981)

The Superior Court relied on Jones v. Montefiore Hosp. to express the division of responsibility between medical experts and juries: medical testimony must establish, with reasonable medical certainty, that the defendant’s conduct increased the risk of the harm sustained; the jury then decides whether the conduct substantially contributed to that harm.

The Supreme Court’s affirmance endorsed that allocation. The expert need not resolve the ultimate factual question by predicting with certainty what would have happened under proper care.

Gradel v. Inouye, 421 A.2d 674 (Pa. 1980)

Gradel v. Inouye reinforced three propositions. First, Section 323(a) relaxes the degree of certainty ordinarily necessary to submit causation to a jury. Second, a medically certain opinion need not be absolute or unqualified. Third, negligence can be a substantial cause even when other causes also contributed.

These principles answered the defendants’ reliance on both the pathologist’s error and the aggressive cancer. Neither necessarily excluded the oncologist’s conduct as another substantial factor. The Court also repeated the principle that a concurrent cause does not relieve a negligent defendant unless that other cause would have produced the injury independently of the defendant’s negligence.

This discussion did not remove the plaintiffs’ ultimate burden of proving causation. It rejected the proposition that identifying another contributing cause automatically defeats the claim.

Mitzelfelt v. Kamrin, 584 A.2d 888 (Pa. 1990)

Mitzelfelt v. Kamrin supplied the ordinary elements of medical malpractice and explained why the usual causation formulation can be impossible to satisfy when some patients would experience the same harm despite appropriate care.

It also established that an expert need not use the exact phrase “increased the risk of harm.” Courts must consider the substance of the testimony as a whole rather than search for a verbal formula.

The present opinion invoked its two-part analysis: whether the complained-of conduct could cause the type of harm suffered, and whether it caused the actual harm in the particular case. The relaxed standard operates in resolving the latter uncertainty. This supported reliance on testimony explaining how delayed lymphoma treatment and unnecessary chemotherapy reduced Smith’s opportunity for a better outcome, even though the expert could not predict her individual response to timely treatment.

Montgomery v. South Philadelphia Medical Group, Inc., 656 A.2d 1385 (Pa. Super. 1995)

This was the defendants’ principal contrasting authority. A patient alleged that a physician’s assistant negligently failed to refer her to a physician after complaints of breast pain. The evidence did not establish when her tumor could first have been detected or whether a physician would have discovered anything beyond the assistant’s findings. The expert offered only conditional possibilities about earlier diagnosis permitting less extensive treatment.

The Supreme Court distinguished that evidentiary gap from the present record. Smith’s lymphoma was demonstrably present in the original tissue. Her oncologist possessed findings inconsistent with the breast cancer diagnosis. The plaintiffs’ causation expert affirmatively testified, to reasonable medical certainty, that the delay deprived her of a substantially better opportunity for a longer life, and explained the medical mechanisms supporting that opinion.

The Court also contrasted the successful recovery described in Montgomery v. South Philadelphia Medical Group, Inc. with Smith’s substantial disease progression and death. The crucial distinction, however, was not death alone: it was the combination of actual harm and sufficiently grounded expert testimony connecting the delayed care to increased risk. The earlier case therefore remained a limit against speculative causation, not a barrier to this claim.

Morena v. S. Hills Health Sys., 462 A.2d 680 (Pa. 1983)

Morena v. S. Hills Health Sys. governed compulsory nonsuit. A court must credit evidence favorable to the plaintiff, draw reasonable favorable inferences, and resolve evidentiary conflicts in the plaintiff’s favor. Nonsuit is appropriate only when the jury could not reasonably find the necessary elements.

At the same time, juries cannot decide cases through speculation or conjecture. This precedent required the Court to distinguish genuine evidentiary insufficiency from disputes about persuasive weight. It concluded that the defendants’ objections largely concerned the latter.

Hicks v. United States, 368 F.2d 626 (4th Cir. 1966)

The Court repeated the policy reasoning from Hicks v. United States quoted in Hamil v. Bashline: a negligent actor who destroys a substantial opportunity for survival cannot demand certainty about the outcome that the negligence prevented from occurring.

This reasoning supported rejection of the demand for a definite account of what a hypothetical pathology consultation would have accomplished. It did not authorize recovery on an unsupported possibility; the plaintiffs still needed competent evidence that the negligence increased the relevant risk.

In re Vencil, 152 A.3d 235 (Pa. 2017)

In re Vencil supplied the standard of appellate review. The legal question received de novo review with a plenary scope, permitting independent consideration of whether the increased-risk doctrine had been correctly applied.

Smith v. Kannarkatt: The intermediate decision and allowance of appeal

The Court discussed the Superior Court’s March 11, 2024 decision in Smith v. Kannarkatt, agreeing with its assessment that the combined expert evidence justified jury consideration. It also cited Smith v. Kannarkatt, 333 A.3d 1263 (Pa. 2025) (per curiam), which defined the question accepted for discretionary review.

That limitation mattered. Whether to abolish or modify the Hamil v. Bashline standard—or whether it applied at all—was outside the accepted question. The appeal concerned its proper application to the evidence.

5. Analysis of the Court’s Legal Reasoning

A. The certainty requirement concerns increased risk, not guaranteed survival

The opinion’s central distinction is between certainty about an increased risk and certainty about an alternative outcome. The plaintiffs’ expert had to offer a medically grounded opinion that the negligent conduct increased the risk of the harm Smith experienced. He did not have to guarantee that correct treatment would have cured her.

Nor did the doctrine eliminate the ultimate preponderance-of-the-evidence burden. The jury still had to decide whether the negligence was more likely than not a substantial factor in producing the harm. Increased-risk evidence supplied a permissible basis for that finding, not a mandatory conclusion.

B. The experts’ testimony supplied complementary links

Standard-of-care expert Gerald Goldklang, M.D., explained that pathology is a diagnostic “gold standard,” but not an infallible one. Oncologists must consider pathology alongside clinical and radiological information, particularly before administering toxic chemotherapy.

His criticism was specific to the information available to Dr. Kannarkatt. The absence of a primary breast tumor, the competing suggestion of lymphoma, and the wording that the pathology was “compatible” with breast origin warranted direct discussion with pathology and possible further testing. He did not condemn reliance on pathology in every case; indeed, he would not have criticized initial treatment based on the report alone before the additional information became available.

Causation expert Robert Soiffer, M.D., supplied the medical consequences of the delay. He explained that inadequately treated cancer may grow, develop mutations, and become more resistant to therapy. Earlier lymphoma-directed treatment could have reduced disease burden and improved the prospects of a successful transplant. The inappropriate chemotherapy also exposed Smith to debilitating effects without adequately addressing her malignancy.

Read together, these opinions supported a coherent causal account: failure to investigate conflicting information contributed to continued inappropriate treatment; delayed appropriate treatment allowed substantial progression and weakened the patient; those developments reduced the opportunity for longer survival. Treating the experts’ testimony in isolation would have obscured that combined evidentiary foundation.

C. Uncertainty about the pathologist’s hypothetical response was not dispositive

The defendants argued that the plaintiffs needed evidence showing that contact with Dr. Wright would actually have changed the diagnosis. They stressed the absence of a separate pathology expert and Dr. Wright’s equivocal testimony about whether further communication would have altered his conclusion.

The Court declined to make proof of that hypothetical exchange a prerequisite on this record. The original samples contained lymphoma, the later information conflicted with the diagnosis, and expert testimony supported both the obligation to investigate and the harmful consequences of delayed treatment.

This is not a universal rule dispensing with expert evidence about diagnostic processes. It is a fact-specific sufficiency holding: the evidence presented allowed a reasonable inference of increased risk without requiring certainty about an unperformed consultation.

D. A poor prognosis did not establish that negligent treatment was harmless

The defense emphasized the rarity and aggressiveness of the lymphoma, its lack of a standard treatment regimen, and Smith’s survival of approximately twenty-one to twenty-two months—within or above averages reported in the small available studies.

Those considerations did not conclusively answer whether Smith could have lived longer with timely care. Population averages describe groups, not the outcome proper treatment would have produced for one patient. Dr. Soiffer acknowledged uncertainty about her individual survival while explaining why earlier appropriate therapy offered a substantially better opportunity.

Consequently, his inability to specify an additional number of months or years did not negate his increased-risk opinion. The Court did not decide the amount of damages or establish a method for valuing a lost opportunity.

E. Multiple contributors could coexist

The defendants characterized the pathologist’s initial misdiagnosis as the true cause and the oncologist’s omission as secondary. The Court rejected that exclusive framing. A later provider’s negligent failure to respond to contradictory evidence may contribute to harm even though another provider initiated the diagnostic error.

The relevant inquiry was not who made the first mistake, but whether Dr. Kannarkatt’s own conduct substantially contributed to the injury. The cancer itself, the pathology error, and the oncologist’s conduct could all be relevant causal factors.

F. Sufficiency and credibility remained distinct

The defendants could challenge Dr. Soiffer’s experience, concessions, interpretation of the literature, and inability to forecast survival. But at the nonsuit stage, the court could not resolve those disputes as though deciding which side’s medical account was more convincing.

On retrial, the defense remained free to cross-examine the plaintiffs’ witnesses and introduce contrary expert testimony, including evidence that the same outcome was likely despite proper treatment. The jury could reject the plaintiffs’ evidence altogether. The ruling established only that the evidence was sufficient to permit—not compel—a liability finding.

6. Potential Impact and Limits

Diagnostic-error litigation

The decision strengthens the application of increased-risk causation where a treating physician allegedly fails to reconcile inconsistent diagnostic information. It confirms that a provider cannot necessarily avoid jury scrutiny by attributing the entire course of treatment to an earlier specialist’s mistake.

Rare diseases and uncertain outcomes

Patients with rare or highly lethal conditions may lack reliable statistics establishing what timely treatment would have achieved. The opinion confirms that such uncertainty is not automatically fatal when competent medical testimony explains how negligent delay increased the risk of the actual injury.

Expert evidence and trial practice

Plaintiffs should present an integrated account linking the alleged breach to delayed protection against disease and explaining the resulting medical disadvantage. Reciting increased-risk terminology is insufficient. Conversely, defendants seeking nonsuit must identify a genuine missing evidentiary link rather than merely emphasize weaknesses that a jury could weigh.

Provider communication

The opinion underscores the potential legal importance of communication when pathology conflicts with other findings. It does not establish a categorical duty to challenge every pathology report or order duplicative testing in every case. The duty evidence here depended on identifiable inconsistencies and the particular treatment circumstances.

Doctrinal boundaries

• The decision applies existing increased-risk doctrine rather than creating an independent claim for every lost possibility of recovery.
• Reasonable medical certainty remains necessary concerning the increase in risk.
• The plaintiffs must connect the increased risk to harm that actually occurred.
• The jury must still find substantial-factor causation by a preponderance of the evidence.
• The opinion does not determine damages, proportional recovery, or final liability.

7. Complex Concepts Simplified

Increased risk of harm

Negligence makes an existing danger more likely to cause injury. A physician need not cause the cancer to worsen the patient’s prospects through delayed treatment.

Reasonable degree of medical certainty

A professionally grounded medical opinion, not a guess. Here, the required opinion concerned increased risk, not guaranteed survival under different treatment.

Substantial factor

A meaningful causal contribution to the injury. The negligence need not be the only contributing cause.

Preponderance of the evidence

The civil burden of showing that a proposition is more likely true than not. This ultimate burden remained unchanged.

Prima facie case

Evidence sufficient to permit a favorable finding if accepted. It allows the case to continue but does not establish that the plaintiff must win.

Compulsory nonsuit

A ruling ending the plaintiff’s case because the evidence is legally insufficient for a reasonable jury to find liability.

Section 323(a)

A Restatement rule concerning negligent performance of services undertaken to protect another person. It supports liability when the negligent performance increases the risk of resulting physical harm.

Clonal evolution

Changes in cancer-cell populations as they grow, potentially producing mutations that make treatment more difficult.

Vicarious liability

Responsibility attributed to an organization for another person’s actionable conduct within the relevant legal relationship. The practice faced this claim based on Dr. Kannarkatt’s alleged negligence.

8. Conclusion

The opinion preserves a distinction essential to medical malpractice law: uncertainty about whether proper treatment would have saved a patient is not the same as an absence of evidence that negligent treatment increased the risk of death.

Because the plaintiffs presented medically grounded evidence connecting an unchallenged, conflicting diagnosis to delayed effective treatment, disease progression, and diminished survival prospects, a jury—not the court on compulsory nonsuit—had to assess substantial-factor causation. The decision reaffirms meaningful jury access while retaining expert-evidence requirements and leaving liability fully contested.