A 78-year-old man with anemia (Hb 9.6 g/dl) and elevated serum immunoglobulin M (IgM 3,577 mg/dl) levels was referred to our hospital. Bone marrow aspiration yielded a dry tap, and bone marrow biopsy revealed the infiltration of CD20 positive lymphoplasmacytic lymphoma cells and myelofibrosis. The patient was diagnosed with Waldenström's macroglobulinemia complicated with myelofibrosis. TGF-β plasma concentration was elevated. Further, after chemotherapy with bendamustine and rituximab, remission of both Waldenström's macroglobulinemia and myelofibrosis was achieved, and TGF-β levels normalized. MYD88 L265P mutation was detected using highly sensitive digital PCR, which compared with currently used direct PCR product sequencing, has a superior sensitivity. The use of digital PCR has additional advantages toward MYD88 L265P detection, particularly when the available amount of sample DNA is limited owing to myelofibrosis.