To date, mutations in a total of 11 genes related to transcription factors and signalling pathways have been described in patients with different subtypes of SM; of note, while some of these genes have been sporadically reported to be mutated in SM (EPHA7 [12,13], FLT3 [29], IKZF1 [13], PIK3CD [12,13], ROS1 [12,13] and TP53 [29]) (Tables S1 and S2), others (e.g., CBL, JAK2, K/NRAS and RUNX1) are recurrently found to be altered in SM, particularly among SM-AHN patients (Table 3). This evidence concerns the gene PIK3CD and systemic mastocytosis.