International staging of sarcoidosis according to Scadding (1967).
| Stage | Radiological changes | Frequency at diagnosis |
| 0 | Normal findings: unremarkable thorax (chest) with extrapulmonary (“outside the lung”) involvement | 10 % |
| I | Bihilary lymphadenopathy (swelling of lymph nodes on both sides of the lung root; 70% of cases are reversible!) | 50 % |
| II | Biiliary lymphadenopathy + incipient lung infiltration/lung involvement (reticulonodular lung pattern). | 25 % |
| III | Pulmonary infiltration; no bihilary lymphadenopathy. | 10 % |
| IV | Pulmonary fibrosis (irreversible) | 5 % |
