Myeloid sarcoma presenting as a colon polyp and harbinger of chronic myelogenous leukemia

Figure 1 Fragments of polypoid colonic mucosa (A) markedly expanded by a hypercellular infiltrate (B) composed of large immature-appearing neoplastic cells with prominent nucleoli (C) (HE stain; 4 ×, 10 ×, 40 ×).

Figure 2 Immunohistochemical studies demonstrate diffuse positivity for CD33 signifying myeloid origin (A), weak, granular CD34 staining highlighting immature cells (B) (strong CD34 staining highlights endothelial cells), and CD117 highlighting scattered large, immature cells (C) (immunohistochemistry; 10 ×, 20 ×, 10 ×).

Figure 3 Bone marrow biopsy shows a hypercellular marrow (A) with myeloid hyperplasia (B) without an increased number of blasts by CD117 (C) (HE; 10 ×, 40 ×; immunohistochemistry; 20 ×).