Further to the two heterozygous KIT mutations V560G (51%) and D816V(52%) that are known to be present in the mastocytosis cell line HMC-1.2, we found an acquired TP53 C277F mutation in 16% of sequencing reads, suggesting that TP53 mutations might develop during passages of KIT mutated cells. The gene discussed is KIT; the disease is mastocytosis.