#00063957

PCH inclusions has been described in AML, CML, MDS, and mixed-lineage leukemias, and may represent a morphologic variant of Auer rods.

We report an interesting case of acute promyelocytic leukemia (APL) with florid PCH inclusions in blasts that are otherwise morphologically distinct from classic hypogranular or microgranular APL. 

A 43 year old man was incidentally found to have pancytopenia (hemoglobin 120 g/L, neutrophil of 0.2 x 10^9/L, platelet 23 x 10^9/L) and rare circulating blasts with giant eosinophilic pseudo Chediak Higashi (PCH) inclusions. Bone marrow biopsy was performed and aspirate showed blasts of 70% (of WBC) with florid PCH inclusions (A-C) and occasional forms with smaller/more abundant granules (D); butterfly nucleus and Auer rods were not identified. Flow cytometry immunophenotypic profile findings were compatible with APL (CD4-, HLA-DR-, CD11b-, CD13+, CD33+, CD117+, CD64+, CD14-/+, CD16-, CD10-, CD19-, CD2-, cMPO+, nTdT-, cCD3-). Molecular analysis confirms PML-RARAa fusion transcript with an uncommon variable form breakpoint (bcr3) which was reflected in cytogenetics in addition to a trisomy 8 (47,XY,+8,t(15;17)(q24;q21)). Myeloid NGS was negative for Tier I/II DNA variants. Clinically, patient did not develop disseminated intravascular coagulation. After initiation on chemotherapy (LoCoco protocol), PCH inclusions (E) and rare Auer rods (F) were seen in segmented neutrophils. Post-induction marrow shows no further leukocyte inclusions and complete hematologic remission.