Cluster of black pearls sign

The "cluster of black pearls" sign refers to a finding on contrast-enhanced CT useful in differentiating sarcoidosis from other causes of lymphadenopathy such as tuberculosis, lymphoma and metastatic adenocarcinoma.

The sign is depicted by the presence of multiple tiny round nodules (1-2 mm) distributed uniformly within whole or part of a homogenously enhancing lymph node in the venous phase on a thin-section contrast-enhanced multidetector CT study. This sign is 83% sensitive, 98% specific, has a positive predictive value of 91% and a negative predictive value of 96% on a per node basis and a sensitivity of 100% on a per patient basis in the diagnosis of sarcoidosis . The presence of the sign should be combined with other signs of sarcoidosis to increase its accuracy.

Caveats:

• study used CT chest and abdomen only, i.e. the sign has not been validated on neck CT
• this sign has only been validated in one study