A 24-year-old male presents with painless cervical lymphadenopathy and B symptoms (fever, night sweats, weight loss). Lymph node biopsy shows scattered large cells with multiple nuclei and prominent nucleoli in a background of small lymphocytes, eosinophils, and plasma cells. The diagnostic cell marked **A** in the diagram is immunophenotyped and found to be CD15+, CD30+, and CD45 negative. Which of the following is the most likely diagnosis?