Pulmonary Pathology (including Mediastinal)

Results:We show identical molecular signature in the original leukemic blasts and the subsequent histiocytic neoplasms in two pediatric patients with TALL.Using FISH, one case had the same biallelic deletion of the CDKN2A (TP16) locus on 9p21, while using next generation sequencing, the other had the same G13D mutation in the NRAS gene.Conclusions: This confirms a common clonal origin and highlights the need to perform appropriate molecular studies in such patients to better understand the mechanism and etiology behind histiocytic neoplasm seemingly born out of other hematopoietic malignancies.