Myeloid sarcomas: a clinicopathologic study of 20 cases

Abstract

Objective: Myeloid sarcoma is a tumoral mass of mature or immature myeloid blasts in extramedullary anatomic locations. It can be seen de novo or in association with acute myeloid leukemia, myeloproliferative neoplasias, or myelodysplastic syndrome. Isolated myeloid sarcoma can be seen as a relapse in cases with allogenic bone marrow transplantation. Although it may involve any tissue in the body, the most common locations are skin, soft tissues, lymph nodes, and the gastrointestinal tract. Immunohistochemically, most cases show myelomonocytic or pure monoblastic differentiation. We reviewed the clinicopathological features of 20 cases of myeloid sarcoma diagnosed in our institute in view of the literature.

Materials and methods: The cases diagnosed between 2005 and 2012 at the Ankara University Faculty of Medicine, Department of Pathology, were selected. Clinicopathological findings including the age and sex of the patients; symptoms; anatomic location; accompanying hematological disease; and the morphological, immunohistochemical, and cytogenetic features of the cases were noted.

Results: Sixteen of the patients were male and 4 were female. The median age at diagnosis was 47 years. The most commonly involved locations were the lymph nodes and skin. Immunohistochemically, eleven cases were of the myelomonocytic and 7 cases were of the myeloid phenotype, whereas 2 cases showed pure monoblastic differentiation. The median follow-up period for the 18 cases with known clinical data was 33 weeks. Five patients died of the disease in an average of 36 weeks.

Conclusion: Myeloid sarcoma is a rare presentation of leukemias, myeloproliferative neoplasias, or myelodysplastic syndrome, composed of immature myelomonocytic cells in extramedullary tissues. It may present with variable morphological and phenotypic features, always creating a challenge in pathological diagnosis.

Figure 1. A, B, D) Diffuse blastic infiltration in the wall of a Morgagni cyst, in the small intestinal mucosa, and in the dermis (H&E 400x, 200x, 400x, respectively). C) Blastic cells (black arrow) intermingled with adenocarcinoma of the colon (H&E 400x). E) Case 16 showed sinusoidal infiltration of the blastic cells mixed with megakaryocytes (black arrow; H&E 400x). F) Angiolymphatic invasion was seen (black arrows; H&E 400x).

Figure 2. A, B) Starry sky appearance and crushing artifact were noted (H&E 100x). C) Granuloma with blastic cell infiltration (black arrows; H&E 100x). D, E) Necrosis (black arrows) and numerous mitoses were found (H&E 200x, 400x, respectively). F) Pleomorphic blastic cells (H&E 1000x).

Figure 3. Immunohistochemical CD34 (A), CD45 (B), MPO (C), CD117 (D), Tdt (E), and CD68 (F) expression of the neoplastic cells (400x, 400x, 400x, 400x, 200x, 400x, respectively).