Complete response of myeloid sarcoma with FIP1L1-PDGFRA -associated myeloproliferative neoplasms to imatinib mesylate monotherapy.

Myeloid sarcoma (MS) is a localized, extramedullary tumor of acute myeloid leukemia (AML) that typically presents either de novo or concomitantly with myeloproliferative neoplasms (MPN), AML and myelodysplastic syndrome. Patients who have MS must be treated with intensive chemotherapy, as are patients with AML, because MS usually progresses to a systemic manifestation and leads to dismal outcomes. FIP1L1-PDGFRA-associated MPN, a subtype of myeloid and lymphoid neoplasm, is characterized by eosinophilia and abnormalities in the PDGFRA, PDGFRB or FGFR1 gene. Fusion of the FIP1L1 and PDGFRA genes activates the tyrosine kinase. As a result, imatinib mesylate (IM) is widely used for the treatment of this disorder. The coexistence of FIP1L1-PDGFRA-associated MPN and MS is extremely rare. Patients with this condition fail to achieve durable remission and long-term survival without a combination of intensive chemotherapy and IM. Here, we report a case of MS and FIP1L1-PDGFRA-associated MPN that was successfully treated with IM monotherapy.