Approach to the Solitary Pulmonary Nodule

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Approach to the Solitary Pulmonary Nodule

• Hrach Ike Kasaryan

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Introduction

• It is estimated that 150,000 patients per year in
  the US present their physicians with a Solitary
  Pulmonary Nodule (SPN)
• 90 of these are found incidentally by
  radiographic studies done for totally unrelated
  diagnostic work ups
• With the advancement in technology and methods in
  CT scanning this number is increasing

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Definition

• SPN is an intraparenchymal lung lesion that is
  lt 3 cm in diameter and is NOT associated with
  atelectasis or adenopathy
• Lesions greater the 3 cm are defined as MASSES

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Why is it concerning?

• SPN are concerning for what they could represent
• The absolute 1 concern is if the SPN is the
  harbinger of a malignancy
• What is more critical is the fact that the
  earlier you diagnose the malignancy the better
  the survival rate will be

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Why is it concerning

• Chest. 1997 Jun111(6)1486-7
• Patients with the best prognosis are those found
  to have stage IA (T1N0M0) disease.
• These patients have a 61 to 75 5-year survival
  following surgical resection
• Radiol Clin North Am 2000 3819  
• Unfortunately they showed that almost 50 of
  patients have extrathoracic spread by the time of
  diagnosis
• these patients only had a 15 5 year survival

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Why is it concerning?

• With these numbers in mind, it is absolutely
  critical to give the SPN the attention it
  deserves
• If it is not worked up properly we will
  effectively push our patients who do carry a
  malignancy with in the SPN from the 75 survival
  into the 15 survival
• That is just unacceptable

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Differential Diagnosis
It is important to note that the majority of SPN
are of a benign etiology
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SO now you have a patient in your office with an
SPN on CXR or CT what do you do?
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Postgrad Med 2003114(2)29-35
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Assessing Growth

• There are three categories to place the patient
  in assessing growth
• No change in two years / or Growth Rate of benign
  nature
• Indeterminate because of no old studies
• Growth Rate of possible malignancy

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No change in two years

• Radiologic stability is the best predictor of a
  benign etiology.
• Since the 1950s it has been well established
  that if the SPN has not grown in 2 years it is
  benign. (JAMA 1958 166210215 )
• If you have old radiographs and can show no
  change in two years, no further work up is needed

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Benign vs. Malignant Doubling Time

• The time it takes for the apparent volume to
  double is referred to as the doubling time
• one doubling in volume is equivalent to the
  nodule diameter increasing by only 26 to 28
• Benign nodules representing acute inflammatory
  changes have a doubling time of less than 20 days
• In contrast, stable granulomas and hamartomas may
  enlarge slowly and have a doubling time of more
  than 500 days

Semin Ultrasound CT MR 200021(2)97-115
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Benign vs. Malignant Doubling Time

• If the SPN has a doubling time of lt20 days or
  gt500 days the patient is in the clear and can be
  followed
• If however the SPN doubling time falls in between
  20 and 500 days the SPN must be assumed malignant
  until proven otherwise and surgical intervention
  is now recommended.

Postgrad Med 1997101(3)145-50
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Malignant Doubling Time

• With the numbers crunch, biopsy in this case is
  not worth the risks because a malignant diagnosis
  would not change resection therapy
• So in this case, surgical resection is highly
  recommended
• If the patient is reluctant or the risk of
  surgery is really high and you would like to be
  sure of diagnosis before going to the OR, than
  biopsy can be undertaken.

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Postgrad Med 2003114(2)29-35
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Indeterminate Growth Rate

• This is where the real dilemma is created and
  every radiological and clinical clue must be
  taken into consideration to make a decision.
• First step is to look at all patterns of the SPN
  and determine if a typically benign or malignant
  pattern can be found

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Spiral CT with IV contrast Enhancement (SCTIE)

• SCTIE the imaging modality of choice for the SPN
  and should be obtained on all newly diagnosed
  SPNs
• A number of benign etiologies for SPNs have a
  characteristic appearance on CT

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Fat

• Fat on CT can be diagnosed benign hamartoma with
  confidence

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Solid or Central Calcification

• A solid calcified SPN is found in association
  with prior granulomatous infection, most commonly
  histoplasmosis or tuberculosis

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Popcorn Calcification

• Popcorn calcification or Chondroid Calcification
  pattern typical of hamartomas

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Speckled or Punctate Calcification

• Speckled or Punctate calcifications represent
  malignant calcification and should not be taken
  as benign

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Eccentric Calcification

• Eccentric Calcification is also a sign of
  malignant potential

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Radiological Findings

• If you have definitive findings suggestive of
  benign pattern than no further work up is needed.
  
• If still no answer after SCTIE or other
  radiologic finding further work up is needed

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No Specific Pattern Found

• With no specific finding, all risk factors must
  be taken into account.
• Trying to milk the SPN for as much information
  you can may help stratify the risk in the patient

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Size

• Size of the SPN can also help out at this point
  to help make a decision
• In general, smaller nodules are more likely to be
  benign and larger lesions
• 80 of benign SPNs are less than 2 cm in diameter
• However, small size is not necessarily reliable
  evidence of benignity because 15 of malignant
  nodules are less than 1 cm in diameter
  approximately 42 are less than 2 cm in diameter

Radiographics 2043, 2000
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Cavitation

• Although cavitation can occur in necrotic
  malignant SPNs, inflammatory lesions can also
  cavitate.
• The thickness of the cavity wall can be helpful
  in distinguishing benign from malignant lesions.
• Cavities with a greatest wall thickness less
  than 5 mm are almost always benign
• whereas most of those with a maximal wall
  thickness greater than 15 mm are malignant

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Cavitation
This is an example of a thick walled cavity which
came back as squamous cell carcinoma.
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Margins

• Smooth, well-defined margins most often indicate
  a benign nodule
• However 21 of malignant nodules have a smooth
  well-defined margin
• a lobulated margin may reflect uneven growth of a
  SPN and can indicate malignancy
• although 25 of benign nodules, particularly
  hamartomas, are lobulated

Radiology 179469, 1991  
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Indeterminate SPN

• After milking the SPN for all its characteristics
  it is now important to milk the patient for all
  relevant information
• Key points include smoking history symptoms
  comorbid conditions (particularly severe
  emphysema) history and type of prior malignancy
  prior infections and environmental exposures.

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N Engl J Med 3482535-2542
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Odds Ratios
Odds Ratio
Odds Ratio

• Age 20-29 0.05 x
• 30-39 0.24
• 40-49 0.94
• 50-59 1.90
• 60-69 2.64
• Nonsmoker 0.15
• lt 30 pk-yrs 0.74

• 30-39 pk-yrs 2
• gt40 pk-yrs 3.7
• Hemoptysis, absent 1
• Hemoptysis, present 5.08
• No prev malig 1
• Prev Malig 4.95

Radiology 1993 186405-413
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Clinical Decision

• Now after evaluating the entire clinical picture
  and clinically identifiable risks its time to
  determine where they fall into Low, Moderate or
  High risk

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Low risk indeterminate SPN

• 30 year old male, never smoked, nodule is lt1cm
  with no previous studies, no environmental
  exposure, found on CT not seen on CXR and no
  specific pattern found
• Can follow for two years
• OH DOC, I FORGOT TO TELL YOU I HAVE SARCOID!!

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Moderate Risk

• Now you have a patient who isnt clearly low risk.
  Maybe older age, questionable smoke or
  environmental history but not quite screaming
  high risk, what to do?
• PET SCAN is now recommended

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PET SCAN

• Positron emission tomography (PET) with
  18-fluorodeoxyglucose (FDG) has proven to be an
  excellent mode of tumor imaging
• Increased activity is demonstrated in cells with
  high metabolic rates, as is seen in tumors and
  areas of inflammation
• It can also tell us about if any metastatic
  disease is present thus altering treatment
• However the spatial resolution of PET is
  currently 7 to 8 mm, and so the imaging of SPNs lt
  1 cm is unreliable
• 1,912 !!!!

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Pet Scan

• Gould et al performed a meta-analysis of the
  literature on pulmonary nodules and masses and
  PET scanning and found an overall sensitivity of
  96.8 and specificity of 77.8 for detecting
  malignancy.
• PET scans also have a 96 sensitivity and 88
  specificity with 94 accuracy in the diagnosis of
  benign nodules

JAMA 2001 285914924  
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Pet Scan

• So depending on the PET Scan result you can base
  your treatment
• If PET is positive than you can refer the patient
  to CT Surgery for resection options
• If PET is negative than can follow

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High Risk Patient

• 68 year old male, 100 pack years of smoking, used
  to work with asbestos, and coughing up blood
• RIGHT TO THE OR for resection.

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Conclusion

• The main point is to make sure you give the SPN
  the respect it deserves.
• With timely diagnosis we can effectively prevent
  morbidity and mortality for our patients
• There is just no excuse for a patient to die
  because we did not work up the patient in a
  timely fashion.

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