A 68-year-old male auto mechanic presents to his primary care physician with a chief complaint of bilateral, painless masses in the neck region of at least 6 months' duration. He has a 120 pack-year smoking history, and his family history includes a father and brother with thyroid cancer. His past medical history is positive for rheumatoid arthritis. On physical examination, the patient is found to have bilateral supraclavicular and cervical lymphadenopathy consisting of matted groups of lymph nodes that were painless to palpation. The patient was afebrile and had experienced an unintentional decrease in weight from 195 pounds to 180 pounds over a 6-month interval. All parameters of the initial complete blood count (CBC) were normal, and the peripheral smear was without morphological abnormality. A chest x-ray film demonstrated hilar adenopathy without any recognizable parenchymal lung lesions. Excisional biopsy of a group of nodes was performed. On microscopic examination there was diffuse effacement of lymph node architecture by a population of relatively uniform cells, averaging 20 to 40 μm in diameter, with round to slightly irregular nuclei and occasional prominent nucleoli. Immunophenotypically, the cells were characterized by the expression of CD45, CD19, CD20, and κ light chains. No T-cell antigens were detected on the abnormal cells. QUESTIONS 1. What pathological processes must be considered in the evaluation of lymphadenopathy? 2. What is the most likely diagnosis based on the available data? 3. What additional studies should be performed before therapy is instituted?

A 68-year-old male auto mechanic presents to his primary care physician with a chief complaint of bilateral, painless masses in the neck region of at least 6 months' duration. He has a 120 pack-year smoking history, and his family history includes a father and brother with thyroid cancer. His past medical history is positive for rheumatoid arthritis. On physical examination, the patient is found to have bilateral supraclavicular and cervical lymphadenopathy consisting of matted groups of lymph nodes that were painless to palpation. The patient was afebrile and had experienced an unintentional decrease in weight from 195 pounds to 180 pounds over a 6-month interval. All parameters of the initial complete blood count (CBC) were normal, and the peripheral smear was without morphological abnormality. A chest x-ray film demonstrated hilar adenopathy without any recognizable parenchymal lung lesions. Excisional biopsy of a group of nodes was performed. On microscopic examination there was diffuse effacement of lymph node architecture by a population of relatively uniform cells, averaging 20 to 40 μm in diameter, with round to slightly irregular nuclei and occasional prominent nucleoli. Immunophenotypically, the cells were characterized by the expression of CD45, CD19, CD20, and κ light chains. No T-cell antigens were detected on the abnormal cells. QUESTIONS 1. What pathological processes must be considered in the evaluation of lymphadenopathy? 2. What is the most likely diagnosis based on the available data? 3. What additional studies should be performed before therapy is instituted? A 68-year-old male auto mechanic presents to his primary care physician with a chief complaint of bilateral, painless masses in the neck region of at least 6 months' duration. He has a 120 pack-year smoking history, and his family history includes a father and brother with thyroid cancer. His past medical history is positive for rheumatoid arthritis. On physical examination, the patient is found to have bilateral supraclavicular and cervical lymphadenopathy consisting of matted groups of lymph nodes that were painless to palpation. The patient was afebrile and had experienced an unintentional decrease in weight from 195 pounds to 180 pounds over a 6-month interval. All parameters of the initial complete blood count (CBC) were normal, and the peripheral smear was without morphological abnormality. A chest x-ray film demonstrated hilar adenopathy without any recognizable parenchymal lung lesions. Excisional biopsy of a group of nodes was performed. On microscopic examination there was diffuse effacement of lymph node architecture by a population of relatively uniform cells, averaging 20 to 40 μm in diameter, with round to slightly irregular nuclei and occasional prominent nucleoli. Immunophenotypically, the cells were characterized by the expression of CD45, CD19, CD20, and κ light chains. No T-cell antigens were detected on the abnormal cells. QUESTIONS 1. What pathological processes must be considered in the evaluation of lymphadenopathy? 2. What is the most likely diagnosis based on the available data? 3. What additional studies should be performed before therapy is instituted?