This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lymphoma and Plasma cell disorder, Subject name: Medicine
With regards to imaging of primary extra nodal lymphomas, in which of the following sites does extra nodal Hodgkin's disease most commonly occur: 
Select and explain. 
A. Spleen, B. Thymus, C. Thyroid, D. Small bowel
B: Thymus
Answer: B: Thymus 
Explanation: At presentation, Hodgkin disease is usually supra diaphragmatic which means thymus is involved due to contiguous spread from one nodal group to the next along the lymphatic pathways. Hence thymus is involved before spleen and other abdominal organs. Thyroid gland is rarely involved in Hodgkin lymphoma.