Rosai-Dorman-Disease is one subgroup of Non-Langerhans cell
histiocytosis with massive lymphadenopathy. It is a generally a benign
and self-limiting disease, but an association to hemato-lymphoid
malignancies or immune diseases is suspected. We present the case of a
6-year old male patient with multifocal extranodal RDD developing a
secondary biphenotypic, treatment-resistant leukemia during treatment.
Hypothysing that RDD and the secondary leukemia could be based on the
same malign clone or on a cancer predispostion syndrome,
whole-exome-sequencing of a saliva sample and leukemic cells were
performed. A common marker of cell lines of histiocytosis and leukemic
blasts has not been found.