A and B, Anteroposterior and lateral views of right humerus of 36-year-old man with primary lymphoma of bone. Despite extensive bone destruction and large soft-tissue mass, patient’s symptoms were mild. Low-power (C) and high-power (D) microscopic appearance of lymphoma. Lymphoma usually should be considered in differential diagnosis of patient with relatively mild symptoms compared with large size of lesion and also should be considered in the differential diagnosis of destructive-appearing diaphyseal lesions.