Among radiologists, errors in diagnosis related to malignant neoplasms of the bronchus is the second most common cause for litigation. Here, we discuss why radiologists miss lung cancer, when this error is considered malpractice, and what can be done to reduce the likelihood of this missed diagnosis.
Any missed diagnosis can be a serious medicolegal problem, and
perhaps one of the most troublesome of these is a missed diagnosis
of lung cancer. In a study of more than 100,000 medicolegal cases,
collected from 1985 to 1995 by a large data sharing organization
and encompassing all medical specialties, actions involving
malignant neoplasms of the bronchus or lung were the sixth most
common. Among radiologists, errors in diagnosis related to
malignant neoplasms of the bronchus were the second most common
cause for litigation, after legal actions arising from malignant
neoplasms of the female breast. Approximately 90% of the alleged
errors in diagnosis of lung cancer occurred on chest radiographs,
5% on CT scans, and 5% on other studies. Forty-five percent
resulted in indemnity payments, which averaged $150,000 (Lori
Bartholomew, Physician Insurers Association of America, personal
In view of these statistics, several questions are relevant: 1)
Why do radiologists miss lung cancer? 2) When is missed lung cancer
malpractice? 3) What can be done to reduce the likelihood of missed
Why do radiologists miss lung cancer?
Factors that contribute to missed lung cancer can be categorized
as arising from observer error, lesion characteristics, or
Observer error is probably the most important factor. Kundel et
al have described three types of observer error.2 A scanning error
occurs if a nodule is not fixated during the 350 msec that a lesion
is focused on the fovea. A recognition error results if a lesion is
scanned adequately but is not detected. A decision-making error
(figures 1,2) is caused by incorrect interpretation of a recognized
abnormality as normal. Among 20 errors by 4 observers who
interpreted 36 chest radiographs with simulated nodules, scanning
errors accounted for 30%, recognition errors 25%, and
decision-making errors accounted for 45% of observer errors.2
Satisfaction of search error, or "tunnel vision," is another
observer error that may contribute to missed lung cancer. This
error occurs if the radiologist is distracted by important but
unrelated radiographic abnormalities, leading to failure to
diagnose a lung cancer (figure 1). A recent study demonstrated
reduced nodule detectability on radiographs with other major
abnormalities as compared with normal radiographs, suggesting that
"tunnel vision" is an important cause of observer error.3
Lesion characteristics contribute substantially to the
likelihood of diagnosing an early lung cancer. For example, the
size of a lesion is of great importance (figure 3). The smallest
lesion that can be visualized on chest radiographs, even in
retrospect, is 4 mm.4 Studies using simulated nodules of 1 cm on
chest radiographs have demonstrated a false negative error rate
ranging from 40% to 87%.1 However, in a retrospective study of
overlooked lung cancer by Austin et al, 31% of overlooked lesions
were greater than 2 cm in diameter.5 Thus, it is clear that lesion
characteristics other than size affect detection of lung
Lesion conspicuity is another crucial factor in the
detectability of lung cancer.1 Conspicuity refers to the extent to
which a lesion is distinguishable from adjacent opacities that may
impair its visibility (or more simply, the extent to which it
"stands out"). The term encompasses both the density of the nodule
itself and the surrounding structures that reduce visibility such
as ribs, clavicles, or blood vessels that project adjacent to or
over the nodule (figure 3). Although lesion conspicuity is a useful
concept, a rigorous definition has not been agreed on.
Technical considerations also may have a role in a failure to
diagnose lung cancer.1 An anteroposterior examination can be a
contributing factor, particularly if portable technique is used. In
the recent study by Latief et al, the mean diameter of overlooked
on anteroposterior radiographs was 2.3 cm.6 Additionally,
patient motion or a suboptimal inspiratory effort increases the
likelihood that a lung lesion will be overlooked. Factors such as
film contrast, density, and kvp also affect lesion detectability
(figure 3). In general, a wide-latitude, low-contrast technique
(130-140 kvp) is preferred because it provides more uniform film
exposure than a low kvp technique.
When is missed lung cancer malpractice?
It has been argued by plaintiff attorneys that any missed lung
cancer constitutes malpractice, but there is compelling evidence in
the radiologic literature that overlooked lung cancer should not
necessarily lead to a successful medicolegal action.7 Muhm et al
used chest radio-graphs to screen for early lung cancer at 4-month
intervals in a large cohort of men who were heavy smokers.8 Of the
50 peripheral lung cancers diagnosed, 45 (90%) were visible in
retrospect on a radiograph taken 4 months earlier. Four cancers
(8%) were visible in retrospect 2 years prior to diagnosis, and one
was visible 53 months earlier. Twelve (75%) of 16 perihilar lesions
also were visible on prior examinations.8 In this study, failure to
diagnose lesions occurred despite a high level of suspicion on the
part of at least two interpreters. This study seems to give weight
to the belief that expecting radiologists to diagnose all lung
cancers is unreasonable.
In general, negligence is the legal criterion that is used to
decide whether malpractice has occurred in cases of missed lung
cancer, or other missed diagnoses.7 Negligence can be proven if a
radiologist breaches the standard of care by failing to diagnose a
lung cancer, and if this failure to diagnose is a proximate cause
of substantial injury to the patient. Although it is possible to
breach the standard of care and not be found liable because of a
lack of proximate cause or substantial injury, it is far easier to
argue that the standard of care was not breached. Unfortunately,
even this defense is not straightforward.
Because there is no rigorous definition as to what constitutes
standard of care in the diagnosis of early lung cancer, the final
decision typically relies on the ability of the experts of each of
the contesting parties to persuade the judge or jury that their
definition is correct. In this endeavor, the conspicuity of a
lesion (as defined above) probably is the single most important
factor in determining whether the standard of care has been
breached. A lesion of high conspicuity (i.e., an "obvious" lesion)
is far more likely to be associated with an adverse legal outcome
than a lesion of lower conspicuity.7
What can be done to reduce the likelihood of missed lung
As is evident from the preceding discussion, complete
elimination of the missed diagnosis of lung cancer is an
unrealistic goal. If radiologists were to lower the threshold for
classifying a finding on chest radiographs as suspicious, observer
error would still result in failure to detect some lesions.
Moreover, the resources required to evaluate every such finding
would be enormous, and the prevalence of lung cancer could be quite
low. Therefore, a more appropriate goal would be to substantially
reduce the rate of overlooked lung cancer, especially among lesions
of high conspicuity.
Several methods of error rate reduction have been suggested. In
the recent study of lung cancer litigation by the Physician
Insurers Association of America, an organization of liability
companies owned or directed by physicians and dentists, a major
factor in the occurrence of overlooked lung cancer was failure to
compare the radiograph on which misdiagnosis was alleged with
pertinent prior examinations.9 Similarly, in a recent study of
missed bronchogenic cancer, failure to compare with one or a
sequence of prior radiographs was the most common cause of
Another approach to decreasing error would be to emphasize the
need to avoid satisfaction of search error, as this appears to be
an important contributor to diagnostic failure in the presence of
unrelated major findings. Finally, the use of two independent
interpreters, or double-reading, has been recommended.10
Unfortunately, the study of Muhm et al, in which two interpreters
were used, showed that even this method does not guarantee a
Missed lung cancer on CT
Missed lung cancer also can occur on CT. Two recent studies have
investigated this problem in 23 patients.11,12 Many of the
overlooked lesions were very small (less than 4 mm). However, some
larger lesions also were missed, particularly those in an
endobronchial location (figure 4). Several lawsuits have arisen as
a result of overlooked lung cancer on CT.
Missed lung cancer remains a serious medicolegal issue despite
widespread awareness by radiologists of the problem. The reasons
for errors are many, but frequently they are due to observer
performance and the specific characteristics of the undetected
lesion. Missed lung cancer is often unavoidable and does not always
result in litigation, but overlooked lesions of high conspicuity
are more likely to be associated with an unfavorable legal outcome.
No approach can be expected to eliminate the occurrence of missed
lung cancer entirely, but rigorous comparison of the current
examination with one or more prior radiographs appears to be
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radiograph sufficient? AJR 168:1339-1344, 1997.
7. Potchen EJ, Bisesi MA: When is it malpractice to miss lung
cancer on chest radiographs? Radiology 175:29-32, 1990.
8. Muhm JR, Miller WE, Fontana RS, et al: Lung cancer detected
during a screening program using four-month chest radiographs.
Radiology 148:609-615, 1983.
9. Physicians Insurers Association of America, Lung Cancer
10. Forrest JV, Friedman PJ: Radiologic errors in patients with
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11. White CS, Romney BM, Mason AC, et al: Primary carcinoma of
the lung overlooked at CT: Analysis of findings in 14 patients.
Radiology 199:109-116, 1996.
12. Gurney JW: Missed lung cancer at CT: Imaging findings in
nine patients. Radiology 199:117-122, 1996.
Dr. White and Dr. Meyer are in the Department of Diagnostic
Radiology at the University of Maryland Medical Center in