How are secondary lung tumors diagnosed?

Updated: Feb 16, 2021
  • Author: Daniel S Schwartz, MD, MBA, FACS; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Secondary lung tumors may be identified when patients are evaluated for symptoms such as chest pain, dyspnea, cough, or hemoptysis or when patients with known primary tumors are being staged for metastases.

A clinical scenario that is not infrequently encountered is an incidental finding of secondary lung cancer of unknown origin, known as adenocarcinoma of unknown primary (ACUP), when patients are undergoing screening chest radiography, computed tomography (CT), or positron emission tomography (PET) with CT.

Radiographically, secondary lung tumors can manifest as discrete nodules (single or multiple), interstitial infiltrate(s), or endobronchial lesions with or without distal atelectasis or postobstructive pneumonitis. They often have a characteristic round appearance on chest radiographs. [4]

Diagnostic strategies for ACUP after the initial clinical and radiologic stepwise evaluation include extensive immunohistochemistry, which may yield a final classifying diagnosis in up to 50% of patients, followed by gene expression (or reverse transcription–polymerase chain reaction [RT-PCR]), which may then be expected to provide additional classifying information in the remaining patients. [5, 6, 7, 8]

The clinical decision to pursue tissue diagnosis depends on whether confirmation of clinical findings would alter treatment. Treatment of secondary lung tumors can be performed for curative intent, to reduce or eliminate tumor burden, or to palliate disease.

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