A 53 year old male presents with an enlarged supraclavicular lymph node, and examination reveals enlargement of the Waldeyer ring of oropharyngeal lymphoid tissue. There is no hepatosplenornegaly. Lymph node biopsy reveals replacements by a monomorphous population of large lymphoid cells with enlarged nuclei and prominent nucleoli. The CBC is normal except for finding of mild anemia. Immunohistochemical staining and flow cytometry of the node reveals that most lymphoid cells are CDl9 CD10=,CD3-, CD15-, and negative (TdT). These findings are most consistent with a diagnosis of