RATIONALE: Myeloid sarcoma (MS) and leukemia cutis (LC) are extramedullary tumors comprising myeloid blasts. They can occur de novo or concurrently with hematological disorders, usually acute myeloid leukemia (AML). AML chemotherapy is generally the initial therapy for MS and LC, and hematopoietic stem cell transplantation (HSCT) can be considered as additional therapy. However, treatment for older patients who are unable to continue intensive chemotherapy is not currently standardized. PATIENT CONCERNS: A 71-year-old Japanese woman was diagnosed with multiple MSs associated with myelodysplastic syndrome (MDS), using bone marrow aspiration and lymph node biopsy. DIAGNOSES: Additionally, LC was diagnosed by skin biopsy. Extramedullary MS and LC lesions were formed by massive infiltration of myeloblastic cells. INTERVENTIONS: Twenty courses of 5-azacytidine (5-Aza) were administrated as maintenance therapy after induction therapy with daunorubicin and cytarabine. OUTCOMES: Myeloblasts decreased in the bone marrow and the LC disappeared after induction therapy. The MSs completely disappeared, except for the palatine tonsil lesion, after 5-Aza maintenance therapy. 5-Aza treatment provided long-term partial response for more than 21 months. LESSONS: 5-Aza was well tolerated and may be a good option for the treatment of MS and LC associated with MDS, especially in older patients who cannot receive HSCT.