Solitary pulmonary nodule

Solitary pulmonary nodule (SPN) is defined as a relatively well defined round or oval pulmonary parenchymal lesion equal to or smaller than 30 mm in diameter. It is surrounded by pulmonary parenchyma and/or visceral pleura and is not associated with lymphadenopathy, atelectasis, or pneumonia ⁹.

Questions to ask when you approach a solitary pulmonary nodule:

• is the lesion solitary?

• is it intrapulmonary?

• is the lesion a nodule?

  • should be a discrete round/oval opacity 4-30 mm in diameter; a lesion >30 mm is defined as a mass, not a nodule

  • should not be linear or angular

Differential diagnosis

There are many causes of solitary pulmonary nodule, including:

• neoplastic

  • malignant

    • bronchogenic carcinoma

    • solitary pulmonary metastasis

    • lymphoma

    • carcinoid tumors

      • bronchial carcinoid tumor

      • peripheral pulmonary carcinoid tumor

  • benign

    • pulmonary hamartoma

    • pulmonary chondroma

    • primary pulmonary meningioma: rare

• inflammatory

  • granuloma

  • lung abscess

  • rheumatoid nodule

  • pulmonary inflammatory pseudotumor: plasma cell granuloma

  • small focus of pneumonia: round pneumonia

• congenital

  • arteriovenous malformation

  • lung cyst

  • bronchial atresia with mucoid impaction

• miscellaneous

  • pulmonary infarct

  • intrapulmonary lymph node

  • mucoid impaction

  • pulmonary hematoma

  • pulmonary amyloidosis

  • normal confluence of pulmonary veins

Mimics

• nipple shadow

• cutaneous lesion (e.g. wart, mole)

• rib fracture or other bone lesion

• vanishing pseudotumor of congestive heart failure

• summation of markings

• artifact

See also

• pulmonary nodules

• coin lesion

• Fleischner society criteria for incidental pulmonary nodules