Myeloid sarcoma: a report of four cases at unusual sites.

Myeloid sarcoma (MS) or granulocytic sarcoma is a rare tumor consisting of myeloid blasts with or without maturation occurring at anatomic sites other than the bone marrow. MS can involve any organ system but shows a predilection for skin, bone, and soft tissues of head and neck region. We report four cases of MS occurring at unusual sites, out of which three were de novo and one was associated with acute myeloid leukemia (AML). Although MS is associated with AML, it can rarely present without any existent hematologic disease. Differential diagnosis of a soft tissue mass should include MS even in the absence of leukemia. Establishment of the correct diagnosis depends on morphologic, histochemical, and immunohistochemical examination.