Systemic mastocytosis with associated myeloproliferative disease and precursor B lymphoblastic leukaemia with t(13;13)(q12;q22) involving FLT3.

Systemic mastocytoses represent neoplastic proliferations of mast
cells. In about 20% of cases systemic mastocytoses are accompanied
by clonal haematopoietic non-mast cell-lineage disorders, most
commonly myeloid neoplasms. A case of systemic mastocytosis
carrying the characteristic mutation at codon 816 (D816V) in the
KIT gene of mast cells, with two concurrent accompanying clonal
haematopoietic non-mast cell-lineage disorders, chronic
myeloproliferative disease, unclassifiable and precursor B
lymphoblastic leukaemia is documented. Both accompanying clonal
haematopoietic non-mast cell-lineage disorders carried the
wild-type KIT gene, but had a novel t(13;13)(q12;q22) involving the
FLT3 locus at 13q12. The chronic myeloproliferative disease,
unclassifiable and the precursor B lymphoblastic leukaemia were
cured by syngenous stem cell transplantation, but the systemic
mastocytosis persisted for more than 10 years. The additional
impact of molecular techniques on the correct diagnosis in
haematological malignancies is highlighted, and evidence is
provided that, apart from internal tandem duplications and
mutations, FLT3 can be activated by translocations.