Pulmonary metastases

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

The lungs receive the entire cardiac output and a rich lymphatic network, making them a common destination for metastatic cancer. Sarcoma, renal, colorectal, breast, thyroid, testicular and many other cancers can spread haematogenously; adenocarcinomas may produce lymphangitic disease, while some tumours seed bronchi or pleura.

The central decision is whether a pulmonary abnormality truly represents metastatic disease and, if so, whether it is one component of widespread cancer or a limited site potentially suitable for metastasis-directed treatment. This requires correlation of imaging, pathology, primary-cancer history and full staging rather than pattern recognition alone.

Patients may be asymptomatic, have cough or haemoptysis from an endobronchial lesion, or develop severe exertional dyspnoea from lymphangitic involvement. A management plan must therefore separate tumour control from urgent complication treatment and from symptom support.

Key points

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.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Haematogenous spread

Many solid tumours shed cells into venous blood, which reaches pulmonary capillaries and produces single or multiple parenchymal deposits.

Lymphatic spread

Breast, stomach, pancreas and other cancers can infiltrate pulmonary lymphatics, causing diffuse septal and peribronchovascular disease.

Direct or pleural extension

Adjacent thoracic malignancy and distant tumours may involve pleura, airways or lung through contiguous growth or serosal dissemination.

Treatment and tumour biology

Primary-cancer subtype, stage, prior therapy and molecular characteristics determine metastatic pattern, tempo and likelihood of isolated lung disease.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Circulating tumour-cell survival
Malignant cells detach, evade immune clearance and lodge within pulmonary vessels or lymphatics, which helps produce the characteristic physiological impairment.
2
Tissue extravasation
Cells cross endothelium, adapt to lung microenvironment and establish microscopic metastatic colonies, thereby altering ventilation, gas transfer or respiratory mechanics.
3
Progressive deposit growth
Angiogenesis and local immune evasion permit nodules, masses, lymphangitic infiltration or endobronchial lesions to expand, thereby altering ventilation, gas transfer or respiratory mechanics.
4
Functional impairment
Extensive burden disrupts ventilation, diffusion and vascular flow, while focal disease may remain physiologically silent, which links the underlying lesion to the observed respiratory dysfunction.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Haematogenous nodules

Multiple, smooth or lobulated rounded nodules in a random distribution, sometimes described as cannonball deposits when large, favour blood-borne spread. Variable size may imply repeated tumour embolisation, but morphology is not pathognomonic.

Solitary pulmonary lesion

A single nodule after cancer treatment may be metastasis, a new lung primary or benign disease. Spiculation, air bronchograms, smoking history, disease-free interval and the primary tumour all influence probability but cannot always replace tissue.

Lymphangitic carcinomatosisRed flag

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.

Endobronchial diseaseRed flag

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.

Pleural involvementRed flag

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.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Thin-section contrast CT chest, abdomen and pelvisFirst step
Why
Characterise lung lesions and establish extracranial disease distribution.
Interpretation and limitations
Review number, size, morphology, cavitation, random versus lymphatic distribution, airway involvement, nodes, pleura and possible primary tumour. Comparison with the oldest and most recent scans is essential.
02
Previous imaging and treatment timeline
Why
Determine growth, disease-free interval and relation to therapy.
Interpretation and limitations
Stability over an appropriate interval may support benignity, while new lesions during infection or soon after immunotherapy require caution. The relevant surveillance interval differs by lesion and tumour, so use the specialist pathway.
03
PET-CT
Why
Assess metabolic distribution when local radical treatment is contemplated.
Interpretation and limitations
PET-CT can identify occult disease or a biopsy target, but small deposits, low-avidity tumours and hyperglycaemia reduce sensitivity; infection and inflammation can be avid. It does not prove histology.
04
Image-guided biopsy or bronchoscopy
Why
Resolve diagnosis and obtain predictive tumour material.
Interpretation and limitations
Choose percutaneous core biopsy for a suitable peripheral target or bronchoscopy/EBUS for airway or nodal disease. Confirm that the sample can distinguish metastasis from lung primary and support current molecular testing.
05
Primary-specific staging
Why
Find disease that changes treatment intent or local-treatment eligibility.
Interpretation and limitations
Brain MRI, liver MRI, bone imaging or other tests are selected according to the primary, symptoms and MDT question. Avoid indiscriminate imaging that will not alter care.
06
Pulmonary function and cardiopulmonary fitness
Why
Estimate risk of surgery, radiotherapy or systemic treatment.
Interpretation and limitations
Spirometry, gas transfer, exercise assessment and cardiac evaluation are tailored to the proposed intervention. Good performance status alone does not guarantee sufficient pulmonary reserve for resection.
07
Acute deterioration screen
Why
Identify reversible complications rather than labelling progression.
Interpretation and limitations
Use oxygenation, ECG, chest imaging, cultures, full blood count, renal profile and CT pulmonary angiography or pleural ultrasound when indicated. Cancer increases thrombotic and infection risk.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

New primary lung cancer

A solitary spiculated lesion, smoking risk and tissue morphology may indicate a separate primary rather than recurrence of the known cancer.

Infection

Bacterial, fungal and mycobacterial nodules are common during cancer treatment; microbiology and temporal response prevent false progression calls.

Treatment-related pneumonitis

Immunotherapy, drugs and radiation can produce nodular, organising or diffuse changes that mimic metastatic spread, while chronology and directed testing distinguish the competing explanation.

Sarcoid-like reaction

Symmetrical nodal and perilymphatic change can arise from granulomatous disease or treatment response; tissue may be needed before restaging.

Pulmonary embolic disease

Cancer-associated embolism or infarction can create symptoms and peripheral opacities without new metastatic burden, with targeted examination and testing used to resolve the uncertainty.

Additional chapter-specific clues

Mimic or treatment effectRed flag

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.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01New nodulesInterrogate lesions in known cancerFirst stepOne or more pulmonary lesions appear during or after treatment of a known malignancy.

1Retrieve the primary pathology, treatment history and serial imaging, then have thoracic radiology describe morphology, distribution and growth rather than accepting the report label alone.
2Stage 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.
3If tissue is needed, biopsy the safest accessible site that can provide adequate histology and molecular material; explicitly consider a synchronous lung primary and infection.
4Return the integrated result to the primary-site and thoracic MDT, document intent, and explain both uncertainty and the next review point to the patient.

02Unknown primaryInvestigate pulmonary metastases without an originImaging suggests secondary lung disease but no primary cancer is established.

1Perform focused history and examination, baseline bloods and contrast CT chest, abdomen and pelvis according to the cancer-of-unknown-primary pathway.
2Avoid broad tumour-marker panels with low specificity; use sex-, symptom- and pathology-directed investigations where the guideline identifies a meaningful role.
3Obtain core tissue from the safest representative site for morphology, immunohistochemistry and relevant molecular tests, conserving material rather than ordering an indiscriminate panel.
4Refer to the cancer-of-unknown-primary team and the most likely site-specific MDT, stopping burdensome investigation when it will not improve treatment choices or patient goals.

03OligometastaticTest suitability for metastasis-directed treatmentLimited lung deposits with controlled or controllable primary disease and no immediately disqualifying spread.

1Confirm the apparent limited burden with high-quality staging and, where uncertainty could change radical intent, pathology or further imaging.
2Assess disease-free interval, primary histology, lesion number and location, mediastinal nodes, technical resectability, radiotherapy constraints and cardiopulmonary reserve.
3Discuss surgery, SABR, thermal ablation, systemic therapy or observation at the appropriate specialist MDT; apply current NHS commissioning criteria rather than a universal lesion-count rule.
4Explain that local ablation treats visible deposits but may not eradicate microscopic systemic disease, and agree surveillance plus a plan for new lesions.

04Acute symptomsTreat the complication in front of youEscalationSudden haemoptysis, hypoxaemia, fever, pleuritic pain, collapse or escalating breathlessness.

1Begin ABCDE assessment, quantify bleeding and oxygen need, and involve acute respiratory, oncology or critical-care teams according to severity.
2Investigate pulmonary embolism, infection, malignant effusion, airway obstruction, treatment pneumonitis and tumour progression in parallel, guided by clinical probability.
3Use bronchoscopic or radiological haemostasis, pleural drainage, antimicrobials, anticoagulation or anti-inflammatory treatment only when the corresponding diagnosis and contraindications support it.
4After stabilisation, revisit cancer intent and symptom priorities rather than allowing an emergency admission to generate an unexamined change to long-term treatment.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Treat metastatic cancer throughout the body, including pulmonary deposits when the tumour is responsive.

Primary-specific systemic anticancer therapy

Use only the live site-specific oncology protocol, incorporating histology, molecular results, organ function, performance status and previous treatment.

There is no generic pulmonary-metastasis regimen. Cytotoxic, targeted, endocrine and immune therapies have distinct infection, marrow, organ and inflammatory toxicities; verify NICE and jurisdictional commissioning.

Relieve distressing cough, pleural pain or breathlessness when cause-directed treatment is incomplete.

Opioid for cancer-related cough or pain

Begin with a low protocol-approved dose and titrate to symptom benefit, prior exposure, frailty and renal function.

Monitor sedation, constipation, nausea and delirium, prescribe supportive medicines where appropriate, and do not let symptom relief delay assessment of major haemoptysis or acute respiratory failure.

Reduce inflammatory or oedematous components when the diagnosis warrants treatment.

Corticosteroid for a defined indication

Use the current specialist protocol only for a specific complication such as treatment pneumonitis, airway oedema or another steroid-responsive process.

Corticosteroids do not routinely treat pulmonary metastases. They can mask infection, worsen glucose control, cause proximal weakness and alter immunotherapy decisions; obtain oncology advice whenever possible.

Treat coexisting pulmonary embolism or deep-vein thrombosis rather than the metastases themselves.

Anticoagulation for confirmed venous thromboembolism

Select agent and dose using the current cancer-associated thrombosis pathway, renal function, platelet count, interactions and bleeding risk.

Major haemoptysis, thrombocytopenia, intracranial disease and impending procedures require urgent specialist balancing. Do not anticoagulate unexplained breathlessness merely because cancer is present.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Respiratory failure

Diffuse lymphangitic or extensive parenchymal disease impairs oxygen transfer and lung compliance, causing progressive hypoxaemia, with severity determined by its extent and the patient's underlying reserve.

Airway obstruction

Endobronchial or hilar deposits can cause lobar collapse, post-obstructive infection and haemoptysis, adding morbidity beyond the initial pulmonary disorder.

Malignant pleural effusion

Pleural involvement blocks drainage and increases permeability, producing recurrent fluid and breathlessness, adding morbidity beyond the initial pulmonary disorder.

Pulmonary vascular obstruction

Tumour emboli or lymphangitic disease can raise pulmonary resistance and cause pulmonary hypertension or right-heart strain.

Treatment-related loss of reserve

Surgery, radiation and systemic therapies may compound tumour-related lung impairment and restrict later treatment options, with severity determined by its extent and the patient's underlying reserve.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Measure symptoms and function alongside imaging: breathlessness, cough, haemoptysis, oxygen need, exercise tolerance, weight and performance status may reveal clinically important change first.
Use the primary-cancer protocol for CT interval and response criteria, keeping the same technique where possible and recognising treatment-related pseudoprogression or inflammatory change.
During systemic therapy, follow regimen-specific blood count, renal, hepatic, cardiac, endocrine and infection monitoring rather than applying a generic metastatic-cancer panel.
After metastasectomy or ablation, monitor procedural complications such as air leak, pneumothorax, radiation pneumonitis or bleeding and retain surveillance within the responsible MDT.
Reassess new respiratory deterioration independently for embolism, infection, pleural fluid, airway obstruction and drug toxicity, even when imaging already documents metastases.
Review goals, treatment burden and escalation preferences as disease tempo changes, ensuring palliative care is available during active oncology treatment.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Multiplicity does not equal certainty

Multiple nodules in a person with cancer make metastases likely, yet fungal infection, septic emboli, rheumatoid nodules and drug effects can mimic spread. Immune state and tempo matter.

A solitary nodule may be curable twice

The lesion could be an isolated metastasis suitable for local treatment or a new early lung primary with different nodal staging and surgery. Preserving that distinction can preserve radical options.

Lymphangitic disease can hide on radiography

Severe exertional hypoxaemia may precede dramatic plain-film change. CT showing septal and peribronchovascular involvement, interpreted with infection and oedema differentials, explains the physiology better.

Biopsy the patient, not the prettiest image

The largest lung nodule is not always the safest target. An accessible node, liver lesion or pleural deposit may yield more tissue with less pneumothorax risk and answer the same question.

Oligometastatic is a clinical state

It includes tumour biology, timing, controlled primary, complete treatability and fitness—not just three or fewer dots on a scan. Current commissioning language must be checked for each proposed modality.

11Common pitfallsFrequent interpretation and management errors.

01
Assuming every new lung lesion in a cancer survivor is metastatic and missing a second primary or treatable infection.
02
Ordering biopsy automatically when imaging is conclusive and tissue would not change care, or avoiding it when radical intent depends on certainty.
03
Using PET avidity as histological proof despite inflammatory false positives and low-avidity tumour false negatives.
04
Calling limited deposits oligometastatic before completing staging and reviewing primary control, nodal disease and technical treatability.
05
Applying a generic chemotherapy concept instead of the primary tumour's current molecular and histological treatment pathway.
06
Attributing abrupt dyspnoea to progression and overlooking pulmonary embolism, infection, effusion or treatment pneumonitis.
07
Offering local ablation as if it treats invisible systemic disease or guarantees cure.
08
Scheduling surveillance without naming which MDT owns results, symptoms and the response to new findings.