Synopsis
Interpret suspected secondary lung disease in its oncological context, distinguish mimics and second primaries, and select proportionate systemic, local or supportive management.
- Pulmonary metastasis is a route and pattern of cancer spread, not one disease; prognosis and treatment are governed mainly by the primary tumour biology, distribution, tempo and patient fitness.
- Haematogenous deposits often appear as multiple rounded nodules of varying size, but solitary nodules, miliary disease, cavitation, endobronchial lesions, lymphangitic carcinomatosis and pleural spread also occur.
- A new pulmonary nodule in a person with cancer is not automatically metastatic: infection, inflammation, treatment toxicity and a synchronous primary lung cancer remain important alternatives.
- Retrieve and compare every previous scan. Growth rate, morphology, distribution and the interval from primary treatment frequently change the differential more than one isolated image.
- Contrast CT of chest, abdomen and pelvis defines burden and searches for disease elsewhere; additional imaging should be directed by the known primary and whether results will change management.
- Obtain tissue when the diagnosis is uncertain and the answer changes therapy, using the safest lesion that yields adequate material; biopsy is not compulsory when imaging and clinical context are conclusive and risk exceeds benefit.
- Diffuse septal and peribronchovascular thickening with disproportionate breathlessness suggests pulmonary lymphangitic carcinomatosis, which can deteriorate quickly despite a modest chest radiograph.
- Systemic therapy follows the primary tumour's current molecular and histological pathway, not a generic lung-metastasis regimen.
- Selected oligometastatic disease may be considered for metastasectomy, stereotactic ablative radiotherapy or another ablative technique after specialist MDT review; a low lesion count alone does not establish benefit.
- Supportive care should address oxygen only for hypoxaemia, cough, pain, haemoptysis, pleural fluid, rehabilitation and advance-care planning while active anticancer options are considered.
Key red flags
Progressive dry cough and marked breathlessness with smooth or nodular interlobular septal and peribronchovascular thickening, preserved architecture and small effusions suggest lymphatic tumour spread. Hypoxaemia can progress rapidly.
Localised monophonic wheeze, recurrent pneumonia in the same lobe, haemoptysis or unexplained lobar collapse raises an obstructing endobronchial metastasis or primary bronchial cancer and warrants bronchoscopy planning.
A new unilateral effusion, pleural nodularity or chest-wall pain may represent metastatic pleural disease. Breathlessness can reflect fluid, trapped lung, embolism or parenchymal burden, so symptom attribution matters.
Fever, immunosuppression, recent radiotherapy, immunotherapy or targeted treatment widens the differential to bacterial or fungal infection, organising pneumonia, pneumonitis and radiation change. A response to assumption-based steroids can obscure both infection and diagnosis.
Investigation priorities
Characterise lung lesions and establish extracranial disease distribution.
Management branches
One or more pulmonary lesions appear during or after treatment of a known malignancy.
- Retrieve the primary pathology, treatment history and serial imaging, then have thoracic radiology describe morphology, distribution and growth rather than accepting the report label alone.
- Stage the rest of the disease with tests selected for that primary and discuss whether confirming lung histology would materially change systemic therapy or local intent.
- If tissue is needed, biopsy the safest accessible site that can provide adequate histology and molecular material; explicitly consider a synchronous lung primary and infection.
- Return the integrated result to the primary-site and thoracic MDT, document intent, and explain both uncertainty and the next review point to the patient.