36 year old, Jemima, is sent for mediastinoscopy with biopsy. During this procedure, a small incision is made immediately above the sternum and a rigid tube is inseed into the chest cavity for visualization of the mediastinum by video camera. Several biopsies of lymph nodes are taken and sent for pathologic examination. In these biopsies, the normal lymphoid tissue has been replaced by a mixed population of morphologically normal cells including histiocytes, lymphocytes, monocytes, plasma cells, and eosinophils. Admixed with these cells are infrequent numbers of large binucleate cells with large prominent eosinophilic nucleoli. Immunophenotyping demonstrates that these cells are positive for CD15 and CD30. The CD15 and CD30 positive cells are most likely which of the following?