garland's triad garland's triad in radiology, garland's triad (also known as the 1-2-3 sign) is the concurrence of reasonably symmetrical bilateral hilar lymphadenopathy and right paratracheal lymphadenopathy seen on a chest radiograph. these features are suggestive of thoracic sarcoidosis. garland's triaddifferential diagnosisthoracic sarcoidosis