The use of HMC-1 mast cells as a pre-clinical model (15) has several advantages: (-i-) the expression of KIT variants frequently found in mastocytosis and other diseases; (-ii-) rapid growth in culture, which allows for high-throughput pharmacological studies; (-iii-) development of tumors in xenograft mouse models for in vivo drug testing; and (-iv-) commercial availability. The gene discussed is KIT; the disease is mastocytosis.