Benign vs malignant pulmonary nodule

Last revised by Henry Knipe on 6 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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