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What is A 41-year-old man presented to the emergency department with a 9-month history of cough, exertional dyspnea, nocturnal diaphoresis, and weight loss of 10 kg. The physical examination revealed painless, massive, discrete, rubbery cervical, supraclavicular and axillary lymphadenopathy. Plain radiography of the chest showed bilateral hilar lymphadenopathy. The serum calcium level was elevated at 16.2 mg per deciliter; serum parathyroid hormone is within normal range.

A diagnostic investigation was performed on him and explain in detail?
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