Chest differential diagnosis
Chest differentials turn on distribution, chronicity, and the presence of cavitation, calcification or consolidation. Every alternative below is paired with the finding that distinguished it in that case.
| Alternative diagnosis | Feature that argues against it | Case |
|---|---|---|
| Actinomycosis | Actinomycosis typically crosses tissue planes to involve the chest wall and pleura with sinus tracts, and it is not characterised by bilateral random nodules. | Pulmonary nocardiosis in HIV |
| Adenoid cystic carcinoma or mucoepidermoid carcinoma | These salivary-type tumours of the airway tend to have a broader base with submucosal infiltration, may destroy cartilage and show higher FDG uptake, rather than a smooth polypoid endobronchial nodule. | Endobronchial carcinoid |
| Allergic bronchopulmonary aspergillosis | ABPA shows central bronchiectasis, mucoid impaction and high IgE with Aspergillus sensitisation, rather than peripheral consolidation without bronchial dilatation. | Chronic eosinophilic pneumonia |
| Allergic bronchopulmonary mycosis | ABPA causes central bronchiectasis with mucoid impaction, high IgE and eosinophilia, but the trachea remains of normal calibre. | Mounier-Kuhn syndrome (tracheobronchomegaly) |
| Alveolar microlithiasis | Alveolar microlithiasis produces a diffuse sand-like micronodular pattern with basal predominance and a black pleura sign, unlike the upper-zone distribution here. | Metastatic pulmonary calcification secondary to haemodialysis |
| Aspergillosis | Invasive aspergillosis produces nodules with a halo sign or a cavitating lesion with an air crescent in immunosuppressed patients, whereas a mycetoma forms within a pre-existing cavity. | Pulmonary tuberculosis |
| Atypical pneumonia | Atypical pneumonia usually shows lower-zone ground-glass opacity and consolidation that resolves with antibiotics, without tree-in-bud nodules, cavitation or calcified nodes. | Pulmonary tuberculosis |
| Bacterial pneumonia | Ordinary bacterial pneumonia produces lobar or segmental consolidation that responds rapidly to antibiotics, rather than multiple cavitating nodules progressing over weeks. | Pulmonary nocardiosis in HIV |
| Bronchial hamartoma | An endobronchial hamartoma contains fat and popcorn calcification and shows no somatostatin receptor uptake. | Endobronchial carcinoid |
| Bronchiectasis | Bronchiectasis alone dilates the peripheral bronchi but does not produce diffuse tracheal enlargement beyond 30 mm or tracheal diverticula. | Mounier-Kuhn syndrome (tracheobronchomegaly) |
| Bronchiectasis | Bronchiectasis shows dilated, thick-walled airways with mucoid impaction, and it may coexist with tuberculosis but does not explain the cavitating consolidation and tree-in-bud pattern at presentation. | Pulmonary tuberculosis |
| Bronchogenic carcinoma | Squamous cell carcinoma or adenocarcinoma of the bronchus is usually larger, infiltrative and intensely FDG-avid with nodal involvement, unlike a small typical carcinoid. | Endobronchial carcinoid |
| Cavitating metastasis | Cavitating metastases are usually multiple and peripheral in a patient with a known primary, and they do not resolve with antibiotic therapy alone. | Pulmonary nocardiosis in HIV |
| Cryptogenic organising pneumonia | Organising pneumonia also responds to steroids but typically shows peribronchovascular or subpleural consolidation with reverse halo signs, and peripheral eosinophilia is absent. | Chronic eosinophilic pneumonia |
| Diaphragmatic eventration | Eventration is a smooth elevation of an intact hemidiaphragm without a focal defect or herniated viscera, and the diaphragm remains continuous. | Bochdalek hernia |
| Diaphragmatic lipoma | A diaphragmatic lipoma is a fat-containing mass confined to the diaphragm without a defect or herniation of abdominal contents. | Bochdalek hernia |
| Drug-related pulmonary fibrosis | Drug-induced fibrosis follows chemotherapy or other agents such as amiodarone and improves or stabilises after withdrawal, and the exposure history differs from paraquat poisoning. | Pulmonary fibrosis due to paraquat poisoning |
| Drug-related pulmonary infiltrates | Drug-induced eosinophilic pneumonia follows a newly started medication and usually resolves after withdrawal, whereas this case has no drug trigger and recurs without steroids. | Chronic eosinophilic pneumonia |
| Foreign body granuloma | A foreign body granuloma occurs after aspiration, contains a radiopaque or non-radiopaque foreign body and produces surrounding inflammatory change, and the patient usually recalls a choking episode. | Endobronchial carcinoid |
| Hypogenetic lung syndrome without scimitar vein | Right lung hypoplasia can occur without anomalous venous return, but the defining feature here is the scimitar vein draining to the inferior vena cava. | Scimitar syndrome with horseshoe kidney and portal vein thrombosis |
| Idiopathic pulmonary fibrosis | IPF produces an identical usual interstitial pneumonia pattern but occurs in older patients without a toxic exposure and progresses inexorably, whereas this fibrosis has a defined herbicide trigger. | Pulmonary fibrosis due to paraquat poisoning |
| Lung carcinoma | Lung carcinoma produces a dominant spiculated mass that enhances and may cavitate, but it does not give bilateral tree-in-bud nodularity or calcified lymph nodes. | Pulmonary tuberculosis |
| Lymphoma | Lymphoma produces bulky, homogeneous lymph node masses that may encase vessels and show restricted diffusion, and it is not associated with generalised marrow hyperplasia. | Extramedullary haematopoiesis |
| Meandering pulmonary vein | A meandering pulmonary vein is an anomalous course of a normally connecting vein and is not associated with right lung hypoplasia, dextrocardia or a systemic arterial supply. | Scimitar syndrome with horseshoe kidney and portal vein thrombosis |
| Metastasis | Metastatic disease destroys bone, produces lytic or sclerotic vertebral lesions and is usually painful and progressive, whereas these masses preserve the bone and expand the marrow. | Extramedullary haematopoiesis |
| Neurogenic tumour | A schwannoma or neurofibroma is a well-defined paravertebral mass that often extends through a neural foramen and enhances intensely, without diffuse marrow expansion or rib widening. | Extramedullary haematopoiesis |
| Nonspecific interstitial pneumonia | NSIP shows more uniform ground-glass opacity and less honeycombing than usual interstitial pneumonia, and it is not associated with a single acute toxic ingestion. | Pulmonary fibrosis due to paraquat poisoning |
| Organising pneumonia | Organising pneumonia shows patchy consolidation and reverse halo signs and responds to steroids, without the progressive honeycombing seen after paraquat. | Pulmonary fibrosis due to paraquat poisoning |
| Parasitic infection | Parasitic pulmonary eosinophilia follows travel to an endemic area and may show migratory infiltrates, and it is associated with specific serology. | Chronic eosinophilic pneumonia |
| Paravertebral abscess | An abscess shows rim enhancement with central fluid, often with discitis and endplate destruction, and the patient has fever and raised inflammatory markers. | Extramedullary haematopoiesis |
| Pleural effusion or empyema | A loculated effusion is fluid density with pleural enhancement and no connection to the abdominal cavity. | Bochdalek hernia |
| Primary and secondary hyperparathyroidism | Hyperparathyroidism alone does not usually produce dense pulmonary nodular calcification, and the biochemical profile in this patient on haemodialysis points to metastatic calcification rather than a parathyroid adenoma. | Metastatic pulmonary calcification secondary to haemodialysis |
| Pulmonary arteriovenous malformation | An arteriovenous malformation shows a direct artery-to-vein shunt with a nidus and early venous filling, without anomalous drainage to the inferior vena cava. | Scimitar syndrome with horseshoe kidney and portal vein thrombosis |
| Pulmonary or pleural tumour | A lung or pleural tumour is a solid mass that enhances and may invade the chest wall, without a diaphragmatic defect or herniated fat and bowel. | Bochdalek hernia |
| Sarcoidosis | Sarcoidosis shows perilymphatic nodules along the bronchovascular bundles and fissures with bilateral hilar lymphadenopathy, rather than centrilobular calcified nodules. | Metastatic pulmonary calcification secondary to haemodialysis |
| Septic embolism | Septic emboli are peripheral, wedge-shaped and cavitary with a feeding vessel, and they occur in patients with endocarditis or indwelling lines, often with positive blood cultures. | Pulmonary nocardiosis in HIV |
| Swyer-James syndrome | Swyer-James syndrome produces a hyperlucent, small lung after childhood bronchiolitis with air trapping and a normal pulmonary venous connection. | Scimitar syndrome with horseshoe kidney and portal vein thrombosis |
| Tracheomalacia | Tracheomalacia causes excessive expiratory collapse of a normal-calibre trachea and is best shown on dynamic imaging, without diffuse enlargement. | Mounier-Kuhn syndrome (tracheobronchomegaly) |
| Tuberculosis | Pulmonary tuberculosis favours the upper lobes with tree-in-bud nodularity, cavitation and calcified lymph nodes, whereas nocardiosis produces multiple random nodules and masses without a tree-in-bud pattern. | Pulmonary nocardiosis in HIV |
| Tuberous sclerosis | Tuberous sclerosis produces thin-walled lung cysts and multifocal micronodular pneumocyte hyperplasia with ground-glass nodules, not densely calcified upper-zone nodules. | Metastatic pulmonary calcification secondary to haemodialysis |
| Williams-Campbell syndrome | Williams-Campbell syndrome is a congenital deficiency of bronchial cartilage that causes cystic bronchiectasis, whereas Mounier-Kuhn syndrome is defined by tracheobronchomegaly with diverticula. | Mounier-Kuhn syndrome (tracheobronchomegaly) |
The confirmed diagnosis of each case is stated on the case page and is not repeated here. Sorted alphabetically; the order says nothing about probability.