Lung cancer differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Overview

Lung cancer must be differentiated from other diseases that cause hemoptysis, cough, dyspnea, wheeze, chest pain, dysphonia, dysphagia, unexplained weight loss, unexplained loss of appetite, and fatigue such as pneumonia, bronchitis, metastatic cancer from a non-thoracic primary site, infectious granuloma, pulmonary tuberculosis, tracheal tumors, and a thyroid mass.

Lung Cancer Differential Diagnosis

The table below summarizes the findings that differentiate lung cancer from the most common other conditions that cause hemoptysis, cough, dyspnea, wheeze, chest pain, dysphonia, dysphagia, unexplained weight loss, unexplained loss of appetite, and fatigue.

Condition/disease	Signs/symptoms	Tests
Pneumonia/bronchitis	Typical symptoms include fever, cough, dyspnea, and chest pain; recurrent pneumonia or bronchitis in a smoker or former smoker should raise the suspicion of lung cancer	CXR is the first test performed; CT imaging can be helpful to evaluate pulmonary masses that might not be well visualised with chest x-ray; bronchoscopy can also be used to assess for endobronchial lesions or to biopsy suspicious pulmonary masses
Carcinoid tumor	Often asymptomatic with normal physical examination; may cause cough, dyspnea, hemoptysis, unilateral wheezing, or post-obstructive pneumonia if the tumor is endobronchial or compressing the central bronchi	CT chest: 80% of carcinoid tumors appear as an endobronchial nodule and 20% as a parenchymal nodule, with smooth, rounded borders and is highly vascularized; flexible bronchoscopy shows raised, pink, vascular, lobulated lesions; endobronchial forceps biopsy is usually required for pathology to be diagnostic; bronchial brushings, sputum specimens, and lavage fluid rarely provide sufficient tissue for a conclusive diagnosis
Metastatic cancer from a non-thoracic primary site	Signs and symptoms depend on the location of the primary tumor and distant disease and may include pain, weight loss, malaise, cough, dyspnea, clubbing, or focal wheezing; physical findings may be present depending on the location and extent of the disease	CT chest shows one or multiple nodules of variable sizes from diffuse micronodular opacities (miliary) to well-defined masses, lesions are often irregular and in the periphery of the lower lung zones; CT/MRI head, CT abdomen and pelvis: extrapulmonary cancers that commonly metastasis to the lung include melanoma, thyroid carcinoma, esophageal cancer; ovarian cancer; sarcomas; and adenocarcinomas of the colon, breast, kidney, and testis; PET-FDG scan shows increased uptake in both primary and distant sites, certain metastatic lesions, such as renal cell carcinoma, have a lower probability of 18-fluorodeoxyglucose (FDG) uptake; CT-guided transthoracic needle aspiration (TTNA) can reveal characteristic malignant cells, pneumothorax complicates 20% to 30% of TTNA procedures, the choice between bronchoscopy and TTNA is based on lesion size, location, risks, and local expertise; biopsy during flexible bronchoscopy and biopsy may show characteristic malignant cells, bronchoscopy has a 100% yield for endobronchial lesions (which are extremely rare in metastatic deposits from other primary tumors)
Infectious granuloma	History may include travel to endemic areas, pet/animal exposures, and specific leisure activities (e.g., caving); may feature cough, dyspnea, hemoptysis, weight loss, fever, joint aches, skin lesions, and night sweats, or no symptoms; many possible causes: Histoplasma capsulatum, Mycobacterium tuberculosis, Coccidioides immitis, Cryptococcus neoformans, Aspergillus, Pseudallescheria boydii, Fusarium species, zygomycetes, and others; non-specific skin findings may be seen in atypical mycobacteria and cryptococcosis; lymphadenopathy may be present with active disease	CT-guided TTNA can be used for diagnostic sampling, pneumothorax complicates 20% to 30% of TTNA procedures, the choice between bronchoscopy and TTNA is based on lesion size, location, risks, and local expertise; CT chest typically shows lesions <2 cm diameter and round with smooth borders, old granulomatous disease may feature central, laminated, or diffuse calcification pattern, mediastinal lymphadenopathy without calcifications is sometimes present, nodules from angioinvasive fungi (e.g., Aspergillus, Pseudallescheria boydii, Fusarium species, and zygomycetes) may demonstrate the "halo sign" (ground-glass opacity surrounding the nodule), occasionally, calcifications can be seen in the spleen or liver; fungal serologies: positive during active infection; flexible bronchoscopy and biopsy can sometimes provide sample for identification and culture and sensitivity of organism; PET: usually negative (<2.5 standardised uptake values), may be positive in active infectious processes
Sarcoidosis	Cough, dyspnea, fatigue weight loss, fever, night sweats, rash, eye pain, photophobia blurred vision, and red eye; pulmonary examination is usually unrevealing; can affect any organ, so physical findings depend on specific organs affected; skin lesions including maculopapular eruptions, subcutaneous nodular lesions, and red-purple skin lesions	CT chest: mediastinal adenopathy often present with sarcoid. Sarcoid nodules have predilection for upper zones, although can be located throughout the lung; flexible bronchoscopy and biopsy can demonstrate presence of non-caseating granulomas; CT-guided TTNA can provide access to material from some lesions inaccessible to flexible bronchoscopy; laboratory markers: ACE elevation may be seen in sarcoidosis but is non-specific
Rheumatoid arthritis	Arthralgias, pain, skin nodules, pleural effusions, pleuritis, joint pain, and deformity	CT chest typically shows lung nodule 3 mm to 7 cm, predominantly in peripheral upper and mid-lung zones, may show cavitation; flexible bronchoscopy and biopsy shows rheumatoid necrobiotic nodule, necrobiotic nodules demonstrate a central zone of eosinophilic fibrinoid necrosis surrounded by palisading fibroblasts, the nodule often centered on necrotic inflamed blood vessels; laboratory markers: patients with lung nodules due to rheumatoid arthritis frequently have high levels of rheumatoid factor, although seronegative cases have been reported
Wegener's granulomatosis	Cough, chest pain, dyspnea, hemoptysis, rhinorrhoea, epistaxis, ear/sinus pain, hoarseness, fever, fatigue, anorexia, weight loss, palpable purpura, painful ulcers, uveitis, upper airway inflammation, and sinus pain	CT chest shows solitary or multiple lung nodules, airways are frequently affected; Flexible bronchoscopy or CT-guided TTNA may show necrotising granulomatous inflammation; laboratory markers: anti-neutrophil cytoplasmic antibody (ANCA), ANCA testing results depend on the extent and severity of the disease
Arteriovenous malformation	Dyspnea is uncommon, may cause hemoptysis, pulmonary bruit, arteriovenous communications, or hemorrhagic telangiectasia in the skin, mucous membranes, and other organs, cyanosis and finger clubbing may be present, eurological symptoms from cerebral aneurysms, cerebral emboli	CT chest shows round or oval nodule(s) with feeding artery and draining vein often identified, most common in lower lobes, multiple lesions in 30% of cases, usually round or oval, ranging from 1 cm to several cm in diameter; pulmonary angiography confirms presence and location of AVMs, identifies feeding arterial and venous structures, in cases of significant hemoptysis, pulmonary angiogram is combined with bronchial artery embolisation; ABG analysis may show decreased pO2 and decreased oxygen saturation when AV flow is severe., in cases of severe systemic AVMs, chronic hypoxemia may cause polycythemia
Amyloidosis	Weight loss, paresthesias, dyspnea, and fatigue are the most common symptoms associated with amyloidosis and are common to all systemic forms; weight loss of >9 kg is common; small vessel involvement can cause jaw or limb claudication, and rarely angina; amyloid purpura is present in about 1 in 6 patients, typically peri-orbital; eyelid petechiae are common; hepatomegaly >5 cm below the right costal margin is seen in 10% of patients and splenomegaly is usually of modest degree	CT chest shows lung involvement characterised by focal pulmonary nodules, tracheobronchial lesions, or diffuse alveolar deposits; serum immunofixation shows presence of monoclonal protein; urine immunofixation shows presence of monoclonal protein; immunoglobulin free light chain assay shows abnormal kappa to lambda ratio
Bronchiolitis obliterans organizing pneumonia (BOOP)	Normally presents as a flu-like illness followed by a second illness lasting 1 to 4 months, with low-grade fever, non-productive cough, malaise, dyspnea, and weight loss; sometimes features pleuritic chest pain and hemoptysis; in most patients, auscultation reveals fine, dry lung crackles; finger clubbing is unusual	CT chest typical features include: patchy "ground-glass" opacities in a sub-pleural and/or peribronchovascular distribution; thickening of bronchial walls and cylindrical dilation; 3 to 5 mm diameter centrilobular nodules or other ill-defined nodules, mediastinal lymphadenopathy, pleural effusions; pulmonary function tests typically show a restrictive pattern; bronchoalveolar lavage (BAL shows a mixed cell pattern, with an increase in lymphocytes, neutrophils, eosinophils, mast cells, foamy macrophages, and occasional plasma cells, CD4+/CD8+ cell ratio is decreased, the ratio of lymphocytes to CD8+ cells is significantly increased; transbronchial lung biopsy in combination with BAL can be a useful approach, prior to possible open biopsy; open lung biopsy is often required for a definitive diagnosis
Pulmonary tuberculosis	Cough longer than 2 to 3 weeks, discolored or bloody sputum, night sweats, weight loss, loss of appetite, and/or pleuritic chest pain	Chest x-ray: primary disease commonly presents as middle and lower lung zone infiltrates, ipsilateral adenopathy, atelectasis from airway compression, and pleural effusion can be seen, reactivation-type (post-primary) pulmonary TB usually involves apical and/or posterior segment of right upper lobe, apicoposterior segment of left upper lobe, or superior segment of either lower lobe, with or without cavitation, as disease progresses it spreads to other segments/lobes; sputum smear: positive for acid-fast bacilli (AFB), sputum may be spontaneously expectorated or induced, and at least 3 specimens should be collected (minimum 8 hours apart, including an early morning specimen, which is the best way to detect Mycobacterium tuberculosis), organisms other than M. tuberculosis, especially on-tuberculous mycobacteria (e.g., M. kansasii and M. avium , may be positive for AFB stain; nucleic acid amplification tests (NAAT): positive for M. tuberculosis DNA or RNA amplification tests for rapid diagnosis, may be used on sputum or any sterile body fluid
Non-Hodgkin's lymphoma (NHL)	Aggressive NHL may present with fever, drenching night sweats, malaise, weight loss, cough, shortness of breath, abdominal discomfort, headache, change in mental status, dizziness, ataxia, pleural effusion, lymphadenopathy, pallor, purpura, jaundice, hepatomegaly, splenomegaly, skin nodules, and abnormal neurological examination, low-grade NHL patients often minimally symptomatic or asymptomatic	CT chest: frequently anterior mediastinum, can determine if mass is cystic or solid and whether it contains calcium or fat, contrast enhancement provides information concerning vascularisation of the mass and relationship to adjacent structures; FBC with differential: shows thrombocytopenia, pancytopenia; Blood smear: shows nucleated red blood cells, giant platelets; lymph node biopsy with immunohistochemistry: shows characteristic cells, preferably obtain excisional or core biopsy to provide information on lymph node architecture; mediastinoscopy: used to sample mediastinal nodes
Hodgkin's lymphoma	Predominantly a disease of young adults; most patients present with a several-month history of persistent adenopathy, most commonly of the cervical chain	Plain chest x-ray: typically shows mediastinal mass/large mediastinal adenopathy; PET scan: involved sites appear fluorodeoxyglucose (FDG)-avid (bright) with PET imaging; lymph node biopsy with immunohistochemistry: the Hodgkin's cell can be a characteristic Reed-Sternberg cell, or one of its variants, such as the lacunar cell in the nodular sclerosis subtype; in nodular lymphocyte-predominant Hodgkin's lymphoma, the characteristic cell is the lymphocytic and histiocytic (L&H) cell, also referred to as a popcorn cell
Thymoma/thymic carcinoma	Approximately 30% of patients with thymoma are asymptomatic at the time of diagnosis; may also present with cough, chest pain, signs of upper airway congestion, superior vena cava syndrome, dysphagia, or hoarseness; may have features of paraneoplastic syndromes associated with thymoma including myasthenia gravis, polymyositis, lupus erythematosus, rheumatoid arthritis, thyroiditis, and Sjogren's syndrome; about 30% of patients have symptoms suggestive of myasthenia gravis (e.g., ptosis, double vision)	Plain chest x-ray: in 50% of the patients, thymomas are detected by chance with plain-film chest radiography; CT chest: 90% occur in anterior mediastinum; Positron emission tomography (PET): may be of value in determining malignancy and extramediastinal involvement; pre-operative biopsy: indicated if there are atypical features or if imaging suggests invasive tumor and patient is under consideration for induction therapy
Bronchogenic cyst	Usually diagnosed in infancy and childhood, although 50% are diagnosed after 15 years of age; Approximately 50% of patients are asymptomatic; in adults, chest pain (often pleuritic) and dysphagia (due to esophageal compression) are the most common symptoms; may also feature recurrent cough and chest infection/pneumonia, superior vena cava syndrome, tracheal compression, and pneumothorax	Two-view chest radiography: typically shows a sharply demarcated spherical mass of variable size, most commonly located in the middle mediastinum around the carina, can appear as a solid tumor or show air-fluid level if cyst is infected or contains secretions; CT chest: frequently middle mediastinum, typically at level of the mediastinum, calcifications may also be seen; MRI: frequently middle mediastinum, typically at level of the mediastinum, T2-weighted images show a homogeneous mass of moderate-to-bright intensity, on T1-weighted images, lesions may vary in intensity depending on protein content of the cyst
Tracheal tumors	Common symptoms include dyspnea, cough, hemoptysis, wheeze, and stridor; less commonly, hoarseness and dysphagia may be present	Plain chest radiographs are generally insensitive for detection of tracheal tumors, clues that may indicate the presence of a tracheal tumour include abnormal calcification, tracheal narrowing, post-obstructive pneumonia, and/or atelectasis; helical CT enables accurate calculation of tumor volumes and can help differentiate mucosal lesions from submucosal lesions; MRI can be useful in assessing extension into surrounding tissue and vascular anatomy; bronchoscopy allows direct visualisation, opportunity for biopsy, and potential for laser treatment
Thyroid mass	Symptoms and signs depend on size of mass; may be visible/palpable as lump on anterior aspect of neck; may present with dysphagia, hoarseness, difficulty breathing, and pain in neck or throat; may also be signs and symptoms of hyper- or hypothyroidism depending on the nature of the mass	Laboratory testing should include thyroid function panel, with TSH, free T4, free T3; I-123 thyroid scan is ordered for patients with overt or subclinical hyperthyroidism a hyperfunctioning (hot) nodule is almost always benign, most nodules are hypofunctioning (cold) (most of these are benign, but malignant nodules are also cold); ultrasound and doppler can be used to define dimensions of thyroid nodules and solid/cystic component(s), features suspicious of malignancy include microcalcifications, a more tall-than-wide shape, hypervascularity, marked hypoechogenicity, or irregular margins, it can also guide fine-needle aspiration, which can reveal malignant cells or cyst fluid; CT neck can evaluate cervical lymph nodes in cases of medullary thyroid cancer, and extension of the scan into the chest can help evaluate a retrosternal thyroid mass

Other conditions that can be mistaken for lung cancer including the following:

• Pneumomediastinum
• Empyema
• Abscess
• Pneumothorax (tension and traumatic)
• Pleural effusion
• Pneumothorax
• Superior Vena Cava Syndrome