Hematologic Malignancies USMLE Step 1 Practice Question

A 35-year-old woman presents to her primary care physician for evaluation of incidental mediastinal and hilar lymphadenopathy discovered on chest imaging obtained for unrelated reasons. She reports no fevers, night sweats, or weight loss. Vital signs are normal. Laboratory studies show a hemoglobin of 13.2 g/dL, WBC of 7,500/μL, and platelet count of 250,000/μL. CT chest demonstrates bulky mediastinal lymphadenopathy with involvement of hilar nodes; the lungs are clear without parenchymal infiltration or effusion. Excisional lymph node biopsy is performed. Histopathology reveals scattered large multinucleated cells with prominent nucleoli and abundant cytoplasm admixed within a rich background of small mature lymphocytes, eosinophils, and plasma cells. The neoplastic cells are CD30+ and CD45-. Which of the following is the most likely diagnosis?