Sarcoidosis is a systemic inflammatory disease of unknown etiology characterized by non-caseating granulomas. Lymphadenopathy is present in over 90% of patients and most commonly involves bilateral hilar and mediastinal lymph nodes. 'Lambda sign' (bilateral hilar + right paratracheal LAP) is the classic thoracic CT finding of sarcoidosis. Sarcoid nodes characteristically do not show necrosis — critically important in differentiating from TB lymphadenitis and malignant LAP. Usually more common in young adults aged 20-40 and in African-American populations. Löfgren syndrome (erythema nodosum + bilateral hilar LAP + fever + arthralgia) is the classic presentation of the acute form.
Age Range
20-50
Peak Age
35
Gender
Female predominant
Prevalence
Uncommon
In sarcoidosis, an exaggerated Th1-type immune response develops against an unknown antigen. CD4+ T-lymphocytes and macrophages activate to form non-caseating granulomas — containing epithelioid histiocytes, giant cells, and peripheral lymphocyte mantle. Granulomas show homogeneous distribution throughout the lymph node — explaining homogeneous enhancement on CT. Absence of necrosis (non-caseating) is the fundamental pathophysiological difference from caseous necrosis in TB and rim enhancement is not expected on imaging. Bilateral hilar predilection results from granuloma accumulation in lymphatic drainage pathways of lungs. In chronic sarcoidosis, granulomas may fibrosis and calcification may develop — but calcification is not expected in acute/active form. On PET-CT, active granulomas take up FDG — activated macrophages and T-lymphocytes are metabolically active.
Symmetric enlargement of bilateral hilar (1, 2) and right paratracheal (3) lymph nodes is the most characteristic thoracic CT finding of sarcoidosis. This triple involvement pattern is also known as Garland triad. Lambda letter-like configuration is observed. Absence of necrosis and symmetry are critical in differential diagnosis.
Bilateral symmetric hilar and mediastinal lymphadenopathy on contrast-enhanced CT. Right paratracheal (4R), bilateral hilar (10R, 10L), and subcarinal (7) stations are most commonly involved — 'lambda (λ) sign' or '1-2-3 sign'. Nodes show homogeneous enhancement, no necrosis. Calcification absent in acute phase, 'eggshell' calcification may develop in chronic sarcoidosis. Surrounding mediastinal fat planes preserved — no perinodal infiltration.
Report Sentence
Bilateral symmetric hilar and right paratracheal lymphadenopathy with homogeneous enhancement; no necrosis or perinodal infiltration detected — consistent with sarcoidosis (lambda sign).
Symmetric, mild-moderate FDG uptake in bilateral hilar and mediastinal nodes on PET-CT (SUVmax usually 3-8). Uptake is symmetric — asymmetric intense uptake suggests lymphoma. Concurrent parenchymal lung involvement may be observed. Extrapulmonary involvement (liver, spleen, parotid, skin, joints) can be evaluated on PET-CT. Panda sign (bilateral parotid + bilateral lacrimal uptake) is specific for sarcoidosis.
Report Sentence
Symmetric, mild-moderate FDG uptake in bilateral hilar and mediastinal lymph nodes (SUVmax: ...) — consistent with sarcoidosis.
Peripheral sarcoid LAP (cervical, axillary, inguinal) shows multiple small-medium sized, hypoechoic lymph nodes. Hilum is usually preserved or mildly narrowed — complete hilum loss is not expected. No necrosis — homogeneous hypoechoic internal structure. Bilateral symmetric involvement is characteristic. Parotid and lacrimal gland involvement can be simultaneously evaluated.
Report Sentence
Multiple, homogeneously hypoechoic lymph nodes without necrosis in bilateral cervical region, consistent with granulomatous lymphadenopathy.
Hilar vascularity is usually preserved or increased on Doppler — peripheral vascularity is not expected. Vascularity increase reflects active granulomatous inflammation. RI is within normal limits or mildly elevated (<0.8). This pattern is similar to reactive LAP and differentiates from malignant LAP.
Report Sentence
Hilar vascularity preserved in lymph nodes with no peripheral vascularity detected — consistent with benign/granulomatous lymphadenopathy.
Mild-moderate diffusion restriction on DWI — ADC usually 1.0-1.4 × 10⁻³ mm²/s (higher than malignant, lower than reactive). Homogeneous ADC distribution — no necrosis or heterogeneity. Intermediate signal intensity on T2. Homogeneous enhancement post-contrast.
Report Sentence
Mild diffusion restriction and homogeneous ADC distribution in lymph nodes on DWI — consistent with granulomatous lymphadenopathy.
Criteria
Bilateral hilar LAP only, no parenchymal lung involvement. 50% of patients. 60-80% spontaneous remission.
Distinct Features
Only hilar and mediastinal LAP on CT. Lung parenchyma clear. Usually asymptomatic or mild symptoms.
Criteria
Bilateral hilar LAP + parenchymal lung infiltration. 30% of patients. Perilymphatic nodules, peribronchial thickening.
Distinct Features
LAP + small perilymphatic nodules (along fissures, bronchovascular bundles) on CT. Galaxy sign (large nodule surrounded by small satellite nodules).
Criteria
Parenchymal lung infiltration present but LAP has regressed. 10-15% of patients. Increased risk of fibrosis development.
Distinct Features
No or minimal LAP on CT, parenchymal nodules and/or fibrotic changes. Chronic sarcoidosis findings.
Distinguishing Feature
HL shows anterior mediastinal mass, very intense FDG uptake (SUVmax >8-15), contiguous spread, and usually asymmetric involvement — sarcoidosis shows bilateral symmetric hilar LAP, low-moderate FDG uptake, and absence of necrosis.
Distinguishing Feature
TB shows rim enhancement (central caseous necrosis), matting, asymmetric involvement, and clinical TB findings — sarcoidosis shows homogeneous enhancement, absence of necrosis, symmetric bilateral hilar involvement, and elevated ACE.
Distinguishing Feature
Reactive LAP has usually smaller size, bilateral hilar involvement is rare, and underlying infection/inflammation history present — sarcoidosis shows prominent bilateral hilar enlargement, parenchymal nodules, and systemic findings (ACE, hypercalcemia).
Distinguishing Feature
NHL shows asymmetric conglomerate LAP, necrosis, extranodal masses, and intense FDG uptake — sarcoidosis shows symmetric hilar LAP, absence of necrosis, and lower FDG uptake.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthSarcoidosis diagnosis requires clinical-radiological-pathological triple correlation. With typical radiological findings (bilateral hilar LAP ± parenchymal nodules) + compatible clinical presentation (young adult, elevated ACE), biopsy demonstrating non-caseating granulomas and excluding other causes (TB, fungal, lymphoma) is needed. Clinical diagnosis may suffice in Löfgren syndrome. Treatment is corticosteroids in symptomatic patients, methotrexate/azathioprine in refractory cases. 60-80% spontaneous remission in Stage I. Follow-up assessed with PFT, CT, and PET-CT.
Sarcoidosis is evaluated with the Scadding staging system: Stage 0 (normal chest X-ray), Stage I (bilateral hilar LAP), Stage II (hilar LAP + parenchymal infiltration), Stage III (parenchymal infiltration, no LAP), Stage IV (pulmonary fibrosis). Spontaneous remission occurs in 60-70% of cases. Treatment is corticosteroids in symptomatic patients. ACE levels are used for monitoring disease activity.