Benign vs malignant pulmonary nodule

Last revised by Henry Knipe on 06 Oct 2022

Differentiating benign from malignant pulmonary nodules is of great importance as it determines the further course of management of the patient.

  • size: the smaller the size the more likely to be benign

    • ~80% of benign nodules are <2 cm in size.

  • margin: smooth, regular; however, ~ 20% of malignant nodules have smooth margins

  • internal characteristics: homogenous attenuation on thin-section CT is seen in ~ 55% of benign nodules vs 20% of malignant nodules

  • smooth, thin-walled cavitary nodules (wall thickness usually <4mm)

  • presence of intranodular fat reliably indicates a benign hamartoma

  • calcification

    • central, diffuse solid and laminated type of calcification are usually seen in prior granulomatosus infections

    • "pop-corn" like calcification is usually seen in hamartoma

  • growth rate

    • doubling time >450 days indicates a benign nodule

    • doubling time <30 days usually represents an acute infection

  • contrast enhancement <15 HU

  • low FDG uptake on PET; however, false negative results can be seen in primary pulmonary malignancies (e.g. adenocarcinoma in situ, carcinoid tumors, other cancers <1 cm)

  • size: the larger the size the more likely to be malignant, however, ~55% are <2 cm in diameter

  • margin: lobulated, irregular or spiculated margins; however, lobulated margins in ~ 25% of benign nodules

    internal characteristics: pseudocavitation is usually seen in adenocarcinoma in situ, while presence of air-bronchogram is suggestive of lymphoma

  • irregular, thick walled cavitary nodules (wall thickness usually >16 mm)

  • calcification: diffuse and amorphous or punctate calcification can be seen in lung cancers or metastases

  • growth rate: doubling time is usually between 30 and 400 days

  • contrast enhancement of >20 HU.

  • increased FDG uptake on PET; however, false positive results can be seen in infectious and inflammatory processes (e.g. active tuberculosis, histoplasmosis, rheumatoid nodules)

  • doubling time refers to the time duration required for doubling of the volume of pulmonary nodul; it results in 26% increase in the diameter of the nodule

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Cases and figures

  • Case 1: pulmonary hamartoma
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  • Case 2: pulmonary cryptococcosis
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  • Case 3: calcified pulmonary metastases
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  • Case 4: cavitating lung cancer
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