CASE PRESENTATION: A 65-year-old Japanese male presented to the previous hospital with two weeks of fever with productive cough. Chest computed tomography (CT) obtained at that hospital showed multiple lung nodules in both lungs and he was diagnosed as having septic pulmonary embolism. Levofloxacin therapy was started, but his fever and radiographic abnormalities persisted in spite of 10 days treatment. He was referred to our hospital for the definitive diagnosis. His past medical history included hepatitis C virus (HCV) related cirrhosis diagnosed 18 years ago which was treated with simeprevir, pegylated interferon alfa 2a plus ribavirin therapy one year before. He had no smoking and had quit drinking alcohol 45 years ago. His medications were as follows: amlodipine, esomeprazole, brotizolam, levofloxacin, loxoprofen and rebamipide. He had no family history and allergic history. Vital signs were as follows: heart rate, 98 bpm; respiratory rate,24 breaths per minute; blood pressure, 133/84 mmHg; temperature, 38.2 degrees Celsius; and oxygen saturation, 99% on room air. Physical examination revealed a lot of untreated tooth decay, and no lymphadenopathy. There were tattoo over his whole body, but no injection scar. Breathing and cardiac sounds were normal. Laboratory test values were as follows: white blood cells, 7,470 /mm3; hemoglobin, 12.2 g/dl; platelets, 169,000 /mm3; serum CRP, 8.65 mg/dl; D-dimer, 2.5 μg/ml; Hepatitis C virus antibody, 15.4 S/CO; tumor markers (CEA, 0.7 ng/ml; CYFRA, 0.7 ng/ml; Pro-GRP, 40.1pg/ml) were within normal limits. Chest x-ray revealed bilateral multiple nodules and on the right middle lung field. Contrast-enhanced whole body CT scan revealed multiple round nodules and masses of varying sizes in both lungs, and these lesions were heterogeneously enhanced. Blood, urine and sputum culture grew no microorganisms. Echocardiography showed normal left ventricular wall movement, no valvular disease and vegetation. The additional test values were as follows: Procalcitonin, <0.1; soluble interleukin-2 receptor, 7753U/ml. The patient had undergone transbronchial lung biopsy (TBLB) of the right middle lung lobe nodule, and pathological examination of TBLB sample revealed middle- to large-sized atypical lymphocytes. Immunohistochemical staining of these cells demonstrated ALK(+), CD30(+), CD3 (+/-), and CD20(-). The patient was diagnosed as having anaplastic large cell lymphoma. The chemotherapy with cyclophosphamide, doxorubicin, vindesine, and prednisone was started, and his condition improved immediately. After 4 cycles of chemotherapy, CT scan demonstrated reduction in number and size of pulmonary nodules.