Clinical characteristics and treatment outcomes of isolated myeloid sarcoma without bone marrow involvement: a single-institution experience

Abstract

Background: Isolated myeloid sarcoma (MS) is a rare extramedullary tumor mass composed of malignant myeloid precursor cells without any evidence of leukemia in the peripheral blood and bone marrow. We describe the clinical characteristics and outcomes of patients diagnosed with isolated MS at our institution.

Methods: We retrospectively reviewed 9 of 497 acute myeloid leukemia (AML) patients (1.8%) with isolated MS. Isolated MS patients were divided into 2 groups according to the first-line treatment strategy: systemic treatment only (S) or local treatment with or without systemic treatment (LS).

Results: The most common site of MS occurrence was the head and neck area (N=4, 44.4%), followed by the anterior mediastinum (N=2, 22.2%) and the gastrointestinal tract (N=2, 22.2%). The tumors of 4 patients (44.4%) eventually evolved to AML, in a median time of 13.4 months (range, 2.4-20.1 mo). The number of patients achieving complete remission after first-line treatment was higher in the LS group (N=5, 83.3%) than in the S group (N=1, 33.3%) (P =0.226). All patients in the LS group survived, but those in the S group died (P=0.012).

Conclusion: Accurate and rapid diagnosis using various modalities and the early initiation of intensive combined treatment may be the optimal strategies to reduce the risk of isolated MS subsequently evolving to AML. To fully understand the characteristics of isolated MS, a larger number of patients from a multinational study is necessary.

Keywords: Acute myeloid leukemia; Myeloid sarcoma; Treatment.

Fig. 1. Computed tomography (CT) findings of 56-year-old woman with primary gingival involvement (A) and 48-year-old man with nasal cavity and naso-oropharynx involvement by myeloid sarcoma (B, C). (A) Contrast-enhanced axial CT scan of the neck shows lytic destruction of the right side alveolar bone. (B) Contrast-enhanced axial CT scan of the neck shows diffuse thickening of the nasal cavity. (C) ¹⁸Fluorine-labeled glucose axial PET scan shows strong focal uptake by the same lesions seen on the CT scan.

Fig. 2. Computed tomography (CT) and magnetic resonance imaging (MRI) findings of a 24-year-old man with involvement of the right orbit by myeloid sarcoma who reported right eye proptosis. (A) Contrast-enhanced axial CT scan of the orbit shows a homogeneously enhancing soft tissue mass in the intra-conal and extra-conal spaces of the right orbit. (B) T1-weighted axial MRI scan of the orbit shows a right orbit mass iso-intense to the periorbital muscle. (C) T2-weighted axial MRI scan of the orbit shows a right orbit mass mildly hyper-intense to the periorbital muscle.

Fig. 3. Magnetic resonance imaging (MRI) findings of a 34-year-old man with involvement of the second lumbar vertebral body by myeloid sarcoma who reported back pain and bilateral leg weakness. (A) Sagittal T1-weighted MRI scan of the spine shows an epidural and paravertebral mass iso-intense to muscle at the second lumbar vertebra level. (B) Sagittal T2-weighted MRI scan of the spine shows an epidural and paravertebral mass iso-intense or mildly hyper-intense to muscle at the second lumbar vertebra level. (C) Axial T2-weighted MRI scan of the spine shows a heterogeneously enhancing epidural mass with enhancement similar to or greater than that of normal muscle.