Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusion: report of two cases with different clinical presentation

Abstract

Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (M/LN-eo-TK) such as PDGFRA, PDGFRB, FGFR1, JAK2, FLT3 rearrangement and ETV6::ABL1 fusion include rare and heterogeneous clinical-pathological entities with some similarities, not always associated with peripheral eosinophilia. Accurate diagnosis and demonstration of the specific genetic substrate have important implications since target therapy is possibly available. Herein we report two cases showing different bone marrow features and clinical presentation. Recognition of eosinophilic granuloblasts prompted genetic analysis that showed PDGFRB (case 1) and PDGFRA (case 2) gene rearrangement. Diagnosis of M/LN-eo-TK may be challenging. Pathologists may be the first professionals to suspect the disorder and should be aware of the therapeutic implication. Accurate BOM marrow evaluation with a panel of immunohistochemical reactions, and specific molecular analyses are required for proper diagnosis.

Keywords: Hypereosinophilia; Myeloid/lymphoid neoplasms; PDGFRA; PDGFRB; TKI.

Figure 1.

(A) Hypercellular bone marrow. Normal hematopoiesis is replaced by a monomorphic proliferation of eosinophil precursors (hematoxylin and eosin stain, original magnification 2X). (B) High power view shows eosinophil precursors as large oval cells with moderate cytoplasm containing cytoplasmic pink-reddish granules and a nucleus with coarse chromatin and indistinct nucleoli. No mature eosinophils are evident (hematoxylin and eosin stain, original magnification 60X). (C) Anti-myeloperoxidase (MPO) immunohistochemical stain is negative in neoplastic eosinophilic precursors. (original magnification 20X). (D) A few enlarged erythroid islands are highlighted in the para-trabecular space (arrow) (hematoxylin and eosin stain, original magnification 20X). (E) Reticulin fiber network is increased (silver stain, original magnification 20X). (F) Expansion of spindle-shaped mast cells which do not form highly cohesive groups. (Anti-tryptase antibody, original magnification 20X).

Figure 2.

(A) Hypercellular bone marrow. Normal hematopoiesis is replaced by a monomorphic proliferation of eosinophilic myelocytes (hematoxylin and eosin stain, original magnification 2X). (B) High power view shows eosinophilic myelocytes as large oval cells with moderate cytoplasm containing cytoplasmic pink-reddish granules and a nucleus with coarse chromatin and indistinct nucleoli (hematoxylin and eosin stain, original magnification 60X). (C) Anti-myeloperoxidase (MPO) immunohistochemical stain (original magnification 20X). (D) Enlarged erythroid islands (arrow) (hematoxylin and eosin stain, original magnification 20X). (E) Reticulin fiber network is increased (silver stain, original magnification 20X). (F) Expansion of spindle-shaped mast cells which do not form highly cohesive groups. (Anti-tryptase antibody, original magnification 20X).