Myeloid sarcoma involving the breast.

CONTEXT: Myeloid sarcoma is a neoplasm of myeloid cells that can arise before, concurrent with, or following acute myeloid leukemia. Rarely, it can also occur as an isolated mass.

OBJECTIVE

To describe the clinicopathologic features of 6 patients with myeloid sarcoma involving the breast.

DESIGN

Clinical information for all 6 patients was obtained from the medical record. Routine hematoxylin-eosin-stained slides; naphthol AS-D chloroacetate stain; and immunohistochemical stains for myeloid, B-cell, and T-cell antigens were prepared.

RESULTS

There were 6 women with a median age of 52 years (range, 31-73 years). Two patients presented with isolated tumors of the breast, with no history or subsequent development of acute myeloid leukemia. In 3 patients, the breast tumors represented relapse of acute myeloid leukemia. One patient who presented initially with myeloid sarcoma involving the breast, skin, and spleen was lost to follow-up. Histologically, these tumors were classified as well differentiated (n = 3), poorly differentiated (n = 2), and blastic (n = 1). Naphthol AS-D chloroacetate esterase was positive in all 3 cases assessed. Immunohistochemistry showed that myeloperoxidase (n = 5) and CD43 (n = 3) were positive, and CD3 (n = 5) and CD20 (n = 5) were negative in all cases assessed. Lysozyme was positive in 4 (80%) of 5; CD117 was positive in 2 (67%) of 3; and single cases were positive for CD45 (1/3), TdT (1/2), CD79a, and the PAX5 gene product.

CONCLUSIONS

Myeloid sarcoma involving the breast is uncommon. In the literature, as in this study, these tumors most often represent relapse or the initial presentation of acute myeloid leukemia. However, 2 of the cases we report presented with isolated masses, without a history or subsequent development of acute myeloid leukemia at last follow-up. Immunohistochemical studies are extremely helpful for recognizing isolated myeloid sarcoma.