Morphologic and immunophenotypic features of the bone marrow biopsy and aspirate. (A) Bone marrow core biopsy shows hypercellular bone marrow with trilineage hematopoiesis and markedly increased eosinophils (H&E, ×200). (B) Bone marrow aspirate smear shows increased eosinophils, black arrows (Wright-Giemsa, ×500). (C) Immunohistochemical stain for CD5 shows a few scattered T cells (CD5, ×500). (D) Immunohistochemical stain for CD117 shows slightly increased atypical spindle-shaped mast cells (black arrows) with interstitial distribution (500) representing subdiagnostic mastocytosis.