Detection of c-kit mutation Asp 816 to Val in microdissected bone marrow infiltrates in a case of systemic mastocytosis associated with chronic myelomonocytic leukaemia

Background/Aims-The occurrence of myeloid leukaemia in patients with system ic mastocytosis is a well recognised phenomenon. However, the pathophysiolo gical basis of such a coevolution has not been clarified. Recent data have shown that the c-kit mutation Asp 816 to Val is detectable in neoplastic ma st cells in most patients with systemic mastocytosis, including those who h ave associated haematological disorders. The aim of this study was to study clonal disease evolution by analysing bone marrow cells from a patient wit h systemic mastocytosis and associated chronic myelomonocytic leukaemia (CM ML) for the presence of this mutation. Methods-The DNA of microdissected bone marrow cells from a patient with sys temic mastocytosis and associated CMML was analysed for the presence of the c-kit mutation Asp 816 to Val by means of HinfI digestion and direct seque ncing of semi-nested polymerase chain reaction (PCR) products. Results-The two neoplasms could easily be identified and discriminated in p araffin wax embedded bone marrow sections by tryptase and chloroacetate est erase staining. A total number of 10 tryptase positive systemic mastocytosi s infiltrates and 10 tryptase negative CMML infiltrates were removed by mic rodissection. As assessed by HinfI digestion and direct sequencing of semi- nested PCR products, the c-kit mutation Asp 816 to Val was detected in five of seven systemic mastocytosis infiltrates and four of six CMML infiltrate s. By contrast, no c-kit mutation Asp 816 to Val was found in bone marrow i nfiltrates in patients with CMML without associated systemic mastocytosis ( n = 20). Conclusion-These data support a monoclonal evolution of systemic mastocytos is and concurrent CMML in the patient studied.