Pulmonary sarcoidosis is a non-caseating granulomatous disease of the lungs. The lung is the most commonly involved organ in systemic sarcoidosis (>90%). It is characterized by bilateral hilar lymphadenopathy (BHL), perilymphatic nodules, upper lobe predominance, and fibrosis in advanced stages. The Scadding staging system (0-IV) determines disease stage based on radiographic findings. It is common in young adults (20-40 years) with a slight female predominance.
Age Range
20-50
Peak Age
35
Gender
Female predominant
Prevalence
Uncommon
Sarcoidosis is a systemic granulomatous disease of unknown etiology — likely developing from an exaggerated Th1 immune response to environmental antigens on a background of genetic predisposition. In the lungs, non-caseating epithelioid granulomas show lymphatic distribution — accumulating along bronchovascular bundles, interlobular septa, and subpleural regions. This perilymphatic distribution appears as perilymphatic nodules on CT and is the most critical distribution feature distinguishing sarcoidosis (perilymphatic) from lymphangitic carcinomatosis (septal) and miliary TB (random). When granulomas become confluent, they form the 'galaxy sign' — a central dense nodule surrounded by satellite micronodules. Granulomas in mediastinal and hilar lymph nodes create bilateral symmetric lymphadenopathy — the '1-2-3 sign' (right paratracheal + bilateral hilar LAP = Garland triad). The lambda sign is the inverted Y/lambda configuration formed by bilateral hilar and left paratracheal LAP in the posterior mediastinum. In advanced stages, granulomas progress to fibrosis — upper lobe retraction, bronchiectasis, and honeycombing develop. On PET-CT, macrophages in active granulomas show high FDG uptake.
The combination of bilateral symmetric hilar lymphadenopathy + right paratracheal lymphadenopathy is called the '1-2-3 sign' or Garland triad (1 = right paratracheal, 2 = right hilar, 3 = left hilar). When this triple lymph node enlargement is found together with perilymphatic micronodules, sarcoidosis is very strongly suspected. This combination is practically not seen so typically in any other disease — lymphoma is usually asymmetric and anterior mediastinal, TB is usually unilateral and necrotic, metastatic LAP is usually asymmetric.
Bilateral symmetric hilar lymphadenopathy — usually accompanied by right paratracheal LAP ('1-2-3 sign' or Garland triad). Lymph nodes are homogeneous, well-defined, and typically non-calcified (in early stage). Eggshell or 'icing sugar' calcification may develop in chronic sarcoidosis.
Report Sentence
Bilateral symmetric hilar and right paratracheal lymphadenopathy is observed (1-2-3 sign / Garland triad), and sarcoidosis should be primarily considered.
Perilymphatic distribution micronodules (1-5 mm) — along bronchovascular bundles, interlobular septa, and subpleural regions. Nodular thickening of fissures ('beaded septa' appearance) is typical. Shows upper and middle lobe predominance.
Report Sentence
Perilymphatic distribution micronodules are seen along bronchovascular bundles, interlobular septa, and subpleural regions in both lungs, consistent with sarcoidosis.
Galaxy sign — central dense nodule or mass surrounded by satellite micronodules. This pattern formed by confluent granulomas resembles a galaxy. It is a typical finding of parenchymal involvement in sarcoidosis.
Report Sentence
Galaxy sign is observed in the lung parenchyma, consisting of a central dense nodule surrounded by satellite micronodules, consistent with sarcoidosis.
Lambda sign — inverted Y or lambda (Λ) configuration formed by bilateral hilar LAP with left paratracheal (or aortopulmonary window) LAP in the posterior mediastinum. This sign describes the sarcoidosis-specific distribution of mediastinal/hilar LAP.
Report Sentence
Bilateral hilar and left paratracheal lymphadenopathy in lambda sign configuration is observed in the posterior mediastinum, suggestive of sarcoidosis.
Upper lobe predominant pulmonary fibrosis in advanced sarcoidosis (Scadding stage IV) — upper lobe volume loss, traction bronchiectasis, linear opacity and honeycombing. Tends to be bilateral and symmetric. Hilar retraction may be seen.
Report Sentence
Pulmonary fibrosis characterized by volume loss, traction bronchiectasis, and reticular opacity in both upper lobes is observed, consistent with advanced sarcoidosis (Scadding stage IV).
Intense FDG uptake in bilateral hilar and mediastinal lymph nodes on PET-CT. FDG avidity may also be seen in parenchymal nodules. Reflects active granulomatous inflammation — used for treatment response assessment and disease activity evaluation.
Report Sentence
Intense FDG uptake is observed in bilateral hilar and mediastinal lymph nodes on PET-CT, consistent with active granulomatous disease (sarcoidosis).
On MRI, hilar and mediastinal lymph nodes typically show low signal intensity on T2 — due to fibrous granuloma tissue. This feature is valuable in differentiating sarcoidosis from lymphoma (T2 hyperintense).
Report Sentence
T2 hypointensity is observed in hilar and mediastinal lymph nodes on MRI, consistent with granulomatous disease (sarcoidosis).
Criteria
Normal chest radiograph — no findings on imaging.
Distinct Features
May have extrathoracic sarcoidosis (skin, eye, joints). Even lung CT may be normal or show minimal findings.
Criteria
Bilateral hilar lymphadenopathy — no parenchymal involvement.
Distinct Features
Most common presentation (50%). Highest spontaneous remission rate at 55-90%. Löfgren syndrome (BHL + erythema nodosum + arthralgia + fever) in young adults is seen at this stage.
Criteria
Bilateral hilar lymphadenopathy + parenchymal infiltration.
Distinct Features
Perilymphatic micronodules, galaxy sign, consolidation or ground-glass opacity seen. Spontaneous remission 40-70%. Corticosteroid treatment often needed.
Criteria
Parenchymal infiltration — no lymphadenopathy (resolved).
Distinct Features
LAP has resolved but parenchymal involvement persists. Spontaneous remission low at 10-20%. Advanced treatment (methotrexate, azathioprine) may be needed.
Criteria
Pulmonary fibrosis — irreversible parenchymal damage.
Distinct Features
Upper lobe predominant fibrosis, traction bronchiectasis, honeycombing, hilar retraction. No remission. Risk of respiratory failure. Lung transplantation may be needed.
Distinguishing Feature
In lymphoma, LAP is usually asymmetric and anterior mediastinal predominant (symmetric bilateral hilar in sarcoidosis). Lymphoma lymph nodes are T2 hyperintense (sarcoidosis T2 hypointense). Parenchymal involvement in lymphoma is mass-like, not perilymphatic. B symptoms (fever, night sweats, weight loss) are prominent in lymphoma. Serum ACE is elevated in sarcoidosis.
Distinguishing Feature
In TB, LAP is usually unilateral and necrotic (central low density) — bilateral symmetric and non-necrotic in sarcoidosis. TB nodules may show cavitation (rare in sarcoidosis). TB distribution is apical and posterior segment predominant — sarcoidosis shows perilymphatic distribution. PPD/IGRA positive in TB, fever and night sweats prominent. Tree-in-bud pattern may be seen in TB (not seen in sarcoidosis).
Distinguishing Feature
In lymphangitic carcinomatosis, interlobular septal thickening is predominant (perilymphatic nodules predominant in sarcoidosis). Metastasis is usually unilateral or asymmetric — sarcoidosis bilateral symmetric. Metastatic LAP is asymmetric and heterogeneous — sarcoidosis homogeneous and symmetric. Known primary malignancy history favors metastasis. Cavitation (especially SCC metastasis) or calcification (osteosarcoma metastasis) may be seen in metastatic nodules — these findings are not expected in sarcoidosis.
Distinguishing Feature
Infectious granulomas (histoplasmosis, coccidioidomycosis) are usually solitary or few — multiple perilymphatic nodules in sarcoidosis. Calcification in infectious granulomas is more common and appears earlier. Clinical context differs in infectious etiology — endemic area history, positive serology. Systemic involvement (skin, eye, joints) and elevated serum ACE in sarcoidosis are distinguishing.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthTreatment of pulmonary sarcoidosis is determined by stage and symptom severity. In stage I, spontaneous remission rate is high (55-90%), so observation is usually sufficient. In stage II-III, corticosteroids (prednisone 20-40 mg/day, 6-12 months) are first-line for symptomatic patients or progressive parenchymal disease. Second-line agents are used for steroid-refractory or intolerant patients: methotrexate, azathioprine, mycophenolate mofetil, or anti-TNF agents (infliximab). In stage IV fibrotic disease, medical therapy cannot reverse fibrosis — symptom management and complication treatment are essential. Lung transplantation is considered for advanced respiratory failure. Definitive diagnosis is histopathological — non-caseating granuloma is demonstrated via transbronchial biopsy, mediastinoscopy, or EBUS-FNA. Serum ACE and 24-hour urine calcium are used for disease activity monitoring. PET-CT is useful for treatment response assessment.
Sarcoidosis enters spontaneous remission in 50% of patients. Stage 1 (BHL only) has the best prognosis. Corticosteroids are first-line treatment when treatment is needed. Advanced stage pulmonary fibrosis (Stage 4) is irreversible. Extrapulmonary involvement (eye, skin, heart, neurosarcoidosis) should be evaluated.