01Purpose and principlesWhat the assessment is for and the core concepts behind it.
A pulmonary nodule is a focal rounded opacity up to 30 mm surrounded by lung, while a larger lesion is termed a mass. Size is only one feature. Spiculation, upper-lobe location, growth, part-solid morphology and associated lymphadenopathy can raise malignancy probability; benign calcification or a typical perifissural lymph-node shape can lower it. Radiography detects some lesions but CT is required to measure, classify density and evaluate multiplicity and associated anatomy.
The UK nodule pathway has historically used BTS 2015 thresholds, volumetry and Brock and Herder risk models. The BTS page now places that guideline in its archive, while current RCR audit material and NICE health-technology discussions still describe NHS use. Probability and ownership principles remain essential, but the archived schedule should not be presented as universally current. Services should use their approved current nodule pathway and escalate discrepancies through respiratory or lung-cancer multidisciplinary review.
Mediastinal widening is a projection of multiple structures, not a diagnosis. Rotation, AP magnification and low inspiration can widen the contour; lymphadenopathy, thyroid enlargement, tumour, aneurysm, acute aortic disease and haemorrhage are genuine causes. The clinical context determines urgency. In suspected lung cancer, contrast-enhanced CT should be performed before biopsy so anatomy and stage guide the safest procedure. In trauma or acute aortic syndrome, CT angiographic technique answers a different time-critical question.
Key points
- Describe a focal lung lesion by size, number, density, margin, calcification, cavitation, growth and relation to pleura, airway, hila and vessels; compare every useful prior study.
- A mass or chest radiograph suspicious for lung cancer enters an urgent cancer pathway; contrast-enhanced CT of chest, lower neck, liver and adrenals should precede biopsy planning.
- Mediastinal widening is non-specific and projection sensitive, yet radiography cannot exclude acute aortic injury: pursue urgent CT when symptoms, trauma or physiology make the diagnosis consequential.
- Separate low-risk incidental nodules from a symptomatic mass; age, smoking, emphysema, prior cancer and nodule morphology modify malignancy probability.
- For incidental nodules, apply the currently adopted multidisciplinary pathway and document its population limits; older BTS nodule guidance is now archived even though live NHS/RCR materials still reference it.
- Communicate unexpected suspected cancer or vascular danger directly, state the next test and responsible team, and use a tracking system for surveillance.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Record maximum dimensions or volume, solid versus subsolid density, margin, calcification, cavitation, pleural relation and growth using comparable thin-section CT.
Spiculation, hilar mass, bronchial cutoff, lobar collapse, persistent focal consolidation or nodal enlargement raises suspected lung cancer and prompts referral.
Confirm projection and rotation, then assess aortic contour, paratracheal stripes, hila and displacement. Plain radiography cannot determine the precise compartment or exclude vascular disease.
Tearing pain, trauma, pulse inequality, neurological deficit, hypotension or pleural blood with mediastinal change requires urgent contrast CT and specialist escalation.
Dense central, laminated or diffuse calcification, fat or a typical perifissural shape can support benignity, but only when morphology and population fit.
Multiple nodules may represent metastases, infection, inflammation or intrapulmonary lymph nodes; immune status, known cancer and symptom tempo change the pathway.
03Method and interpretationA systematic approach to the test and its findings.
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 chest CTFirst step - Why
- Characterise a radiographic nodule or mass and define size, density, margins, growth, airways, nodes and pleura.
- Interpretation and limitations
- Compare prior CT with consistent technique and use volumetry where validated; management depends on morphology, population and malignancy probability.
- 02
Contrast-enhanced CT before tissue sampling - Why
- Map a suspected lung primary, lower neck, mediastinum, liver and adrenals and identify the safest staging target.
- Interpretation and limitations
- NICE recommends this CT before biopsy; select subsequent bronchoscopy, EBUS, percutaneous or metastatic-site sampling to maximise diagnosis and stage.
- 03
PET-CT - Why
- Refine metabolic probability and stage selected potentially treatable lung cancer or higher-risk nodules.
- Interpretation and limitations
- Inflammation can be avid and small or indolent tumours can be falsely negative; interpret with CT morphology and use tissue when it changes treatment.
- 04
Bronchoscopy, EBUS or percutaneous biopsy - Why
- Obtain diagnosis and nodal stage from the safest highest-yield site.
- Interpretation and limitations
- Procedure choice follows cross-sectional imaging, airway relationship, node accessibility, pneumothorax risk and the information needed for treatment.
- 05
CT angiography of the thoracic aorta - Why
- Evaluate suspected acute aortic injury or syndrome presenting with mediastinal abnormality.
- Interpretation and limitations
- Use an emergency vascular protocol and maintain resuscitation; a non-angiographic chest CT or negative radiograph may not answer the question.
04Clinical next stepsHow the result changes management or prompts escalation.
01Worked case: new hilar massMove from radiograph to diagnosis and stageFirst stepA smoker with weight loss has a chest radiograph showing a new spiculated hilar mass and lobar collapse.+
- 1Communicate the suspicious finding and enter the suspected lung-cancer pathway rather than arranging unowned routine follow-up.
- 2Obtain contrast-enhanced CT of chest, lower neck, liver and adrenals before biopsy to map tumour, nodes, metastases and a safe target.
- 3Use multidisciplinary review to select bronchoscopy, EBUS, percutaneous biopsy or another site that can establish diagnosis and the highest relevant stage.
- 4Verify that results, tissue plan and follow-up responsibility are communicated to the patient and referring team without pathway gaps.
02Incidental noduleApply a population-matched pathwayA small pulmonary nodule is found incidentally on CT in an otherwise stable adult.+
- 1Confirm age, symptoms, smoking, emphysema, previous cancer, immune status, nodule type and prior imaging before applying any algorithm.
- 2Use the service’s approved current nodule guideline and risk calculator, documenting size or volume, morphology and exact interval or discharge decision.
- 3Create a named tracking process; refer to the lung nodule or cancer MDT when morphology, growth or population falls outside the routine pathway.
03Acute mediastinal concernWidening with pain or traumaA patient with acute severe pain or significant trauma has an apparently widened mediastinum.+
- 1Assess physiology and confirm whether projection or rotation could contribute, while keeping aortic injury and haemorrhage active.
- 2Proceed to urgent contrast CT or CT angiography when stable enough and use only minimal imaging to direct intervention when unstable.
- 3Communicate vascular danger immediately and involve trauma, cardiothoracic or vascular services according to the result.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- For any surveilled nodule, record the guideline used, population fit, interval, imaging technique and responsible team.
- Compare growth by validated diameter or volume methods on technically comparable CT; apparent change near measurement limits may need expert review.
- Escalate new symptoms, suspicious morphological change or significant growth rather than waiting automatically for the next scheduled scan.
- Track tissue, PET-CT and staging results through multidisciplinary review until diagnosis and treatment intent are established.
- Audit acknowledgement and completion of suspected-cancer referrals and incidental-finding surveillance because written recommendations can otherwise be lost.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
A nodule is a population problem
The same morphology has different significance in a healthy adult, a child, an immunosuppressed patient and someone with known cancer.
Volumetry detects three-dimensional change
Volume may reveal growth before one diameter changes clearly, but segmentation and acquisition differences create measurement variation.
Biopsy follows staging anatomy
The best target may be a node or metastasis rather than the lung mass when it establishes diagnosis and the highest treatment-relevant stage safely.
Width is projection dependent
AP magnification and rotation can widen the mediastinum, so contours must be interpreted with technique and the clinical probability of vascular disease.
Ownership prevents delayed cancer
A precise interval and named responsible service matter as much as recognising the nodule because surveillance failure converts uncertainty into harm.
07Common pitfallsFrequent interpretation and management errors.
- 01
Applying an incidental adult nodule schedule to a child, known-cancer patient or suspected infection without checking scope.
- 02
Using an archived threshold table as universal current guidance despite a changed local or national pathway.
- 03
Biopsying a lung mass before contrast CT defines nodes, metastases and a safer higher-stage target.
- 04
Dismissing mediastinal widening as rotation when acute symptoms or trauma make aortic disease plausible.
- 05
Recommending follow-up without a named owner, alert, acknowledgement or process for non-attendance.