Myeloid Lineage-Associated Mutations Are Detected in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare but highly aggressive hematologic malignancy that frequently presents with skin, lymph node, and leukemic disease. Since BPDCN can evolve into acute myelomonocytic leukemia (AMML) with other cases associated with monocytosis, a close relationship of BPDCN to the myelomonocytic lineage is suspected. Here we investigate the frequency of myeloid-associated DNA mutations in BPDCN using a targeted exon sequencing panel.

Nine cases of BPDCN (5 skin, 1 lymph node, 3 bone marrow clot sections) were studied. All showed blastic cytomorphology; characteristic expression of CD56 and CD123; CD4 and/or TCL1 expression; and absence of definitive lymphoid, myeloid, and monocytic marker expression. AMML recurrence at 18 months, seen in 1 patient, was also assessed. Genomic DNA was extracted from formalin-fixed paraffin-embedded sections and subjected to a 161-amplicon PCR-based DNA sequencing assay that includes the commonly mutated areas of KRAS, NRAS, IDH1, IDH2, TET2, EZH2, JAK2, and ASXL1. Limited multiplex PCR and product harvesting was performed on an Access Array chip (Fluidigm). Ion adaptors were added and DNA sequencing was performed on a PGM sequencer using the 316 chip with 200 base-pair sequencing chemistry (Life Technologies). Sensitivity of mutation detection varied between 5–10%. Sequencing data were analyzed by SeqNext software (JSI MedSystems). Detected mutations were confirmed using conventional Sanger sequencing, with an approximate sensitivity of 15%, or pyrosequencing (5%).

Mutations in one or more of the tested genes were found in 6 of 9 patients, with unconfirmed mutations in 2 additional cases due to low-level mutations in samples with poor quality DNA. One patient with a typical BPDCN showed an IDH2 mutation (R140Q) with recurrence as AMML showing this mutation as well as a double mutation in KRAS (G12R, Q61R). Other mutations identified included 3 in ASXL1 including W608C, NRAS G12D, EZH2 C-terminal truncation, and 2 TET2indels.

The presence of myeloid-associated mutations particularly in IDH2, TET2 and ASXL1 in cases of BPDCN is support for a relationship to the myelomonocytic lineage. The presence of shared and new mutations in the AMML recurrence in 1 patient with BPDCN further indicates a pathogenetic relationship between the two entities.

Wang:Quest Diagnostics: Employment. Windham:Quest Diagnostics: Employment. Billouin-Frazier:Quest Diagnostics: Employment. Jones:Quest Diagnostics: Employment.