A 45-year-old man came to the hematologist with complaints of general weakness, elevated body temperature, excessive sweating, enlarged cervical lymph nodes. Objectively, his body temperature is 37.5°C, the skin is palezand dry, the posterior cervical lymph nodes are dense and elastic, up to 2 cm in diameter, mobile. There are no peculiarities in the patient's heart and lungs. Hepatosplenomegaly was detected. What examination is necessary to determine the scope of the pathologic process?