Figure 2.

Organ system algorithm for localizing tissue origin. For the cases predicted with non-low risk scores, a k-nearest neighbor based organ system algorithm was used for localizing tissue origin. The performance of a different number of origins is evaluated. When only one possible tissue origin (i.e., top 1) is reported, the sensitivity is low, but specificity is high. In contrast, the sensitivity increases, and specificity decreases when more possible tissue origins (e.g., top 10) are reported. A balanced sensitivity and specificity of the algorithm can be achieved when the top three possible organ systems are reported.