Clinical characteristics and outcomes of isolated myeloid sarcoma without bone marrow involvement: An experience from a tertiary cancer care center in India.

Background: Myeloid sarcoma (MS) refers to extramedullary proliferation of blasts of myeloid lineages that disrupts the normal architecture of the tissue in which it is found. Due to its rarity, prognostic factors and optimal management are yet unknown.

Materials and methods: Medical records of patients diagnosed with MS without marrow involvement and with no history of previous acute myeloid leukemia (AML) were retrieved. Diagnosis was made by immunohistochemical analysis of fixed paraffin tissue. Clinical features and treatment outcomes were recorded. Our aim was to study the clinical features and outcomes of cases of isolated MS diagnosed at our institute from 2010 to 2018.

Results: Ten cases of isolated MS were diagnosed between 2010 and 2018. Median age was 29 years. Common sites of disease were soft tissues (40%) and lymph nodes (30%). Two patients refused treatment, one patient was treated with surgery followed by radiotherapy, and seven patients were treated with intensive chemotherapy. Also, 57.1% had complete response and 28.6% had partial response. The median survival for the entire cohort was 6.5 months. The median progression-free survival (PFS) and overall survival (OS) of patients treated with chemotherapy were 7 and 8 months, respectively.

Conclusion: Isolated MS is a rare presentation of AML. It has a better prognosis than MS with concomitant marrow involvement. Systemic chemotherapy is an essential component of treatment, but the optimal timing is debatable, that is, at diagnosis or if it can be safely deferred until relapse.