Kaposi's Sarcoma in Children After Hematopoietic Stem Cell Transplantation: Two Cases of Rare Primary Tumor Localizations in the Lungs and Lymph Node.

Kaposi's sarcoma (KS) is a vascular / mesenchymal tumor with an indefinite degree of malignancy, caused by complex etiopathogenetic factors including Human Herpes Virus-8 infection of immunocompromised patients. For example, KS is more common in adult men with HIV. We describe 2 very rare cases of iatrogenic KS in children after hematopoietic stem cell transplant with isolated organ damage (case 1: lung; case 2: inguinal lymph node). KS is a potential complication of bone marrow transplant in pediatric patients and can occur in different age groups and at atypical sites.

Molecular characteristic of acute leukemias with t(16;21)/FUS-ERG.

T(16;21)(p11;q22)/FUS-ERG is a rare but recurrent translocation in acute leukemias and in some types of solid tumors. Due to multiple types of FUS-ERG transcripts, PCR-based minimal residual disease detection is impeded. In this study, we evaluated a cohort of pediatric patients with t(16;21)(p11;q22)/FUS-ERG and revealed fusion gene breakpoints. We implemented next-generation sequencing (NGS) on long PCR amplicons for the detection of fusion genes with unknown partners or DNA breakpoints. That allowed us to describe different fusion variants of FUS/ERG in different patients and to detect MRD on both RNA and DNA levels. We also found several accompanying mutations in epigenetic regulators (DNMT3A, ASXL1, BCOR) by targeted NGS approach in AML cases. These mutations preceded full transformation by t(16;21)(p11;q22)/FUS-ERG and allowed us to trace clonal evolution on all steps of therapy. As a casual observation, the ASXL1 mutation was found in the unrelated donor hematopoietic cells.