Garola and Singh propose utilizing a combined score of p16, Ki-67, and HMB-45 (PKH score) to differentiate between SN, AST, and SM: a PKH score <4 in this study appears to be significantly associated with SN and AST, while a PKH score >4 is associated with a diagnosis of SM (70). This evidence concerns the gene CDKN2A and systemic mastocytosis.