**Question:** All are true of Hodgkin lymphoma except -

A. Hodgkin lymphoma is a type of non-Hodgkin lymphoma
B. Hodgkin lymphoma primarily affects children
C. Hodgkin lymphoma is caused by Epstein-Barr virus infection
D. Hodgkin lymphoma usually presents with a single site involvement

**Correct Answer:** B. Hodgkin lymphoma primarily affects children

**Core Concept:**
Hodgkin lymphoma is a type of non-Hodgkin lymphoma, which is a group of cancers that affect the lymphatic system. Non-Hodgkin lymphoma is further classified based on the involved cell type and the presence of specific cell markers. Hodgkin lymphoma, on the other hand, is characterized by the presence of distinctive Reed-Sternberg cells in the affected tissues.

**Why the Correct Answer is Right:**
Hodgkin lymphoma primarily affects adults, particularly those aged between 20 and 40 years. While it can occur in children, it is much less common. The disease is named after Thomas Hodgkin, who first described the disease in 1832 and not because it primarily affects children.

**Why Each Wrong Option is Incorrect:**

A. Hodgkin lymphoma is a type of non-Hodgkin lymphoma, not a non-Hodgkin lymphoma. This option is incorrect because it contradicts the definition of Hodgkin lymphoma as a specific type of lymphoma, not a subtype of non-Hodgkin lymphoma.

C. Hodgkin lymphoma is caused by Epstein-Barr virus infection. While Epstein-Barr virus is implicated in the pathogenesis of some cases of Hodgkin lymphoma, the virus is not the primary cause of the disease. Instead, it is a cofactor that facilitates the development of the disease in genetically susceptible individuals.

D. Hodgkin lymphoma usually presents with multiple site involvement, not single site involvement. In general, Hodgkin lymphoma often spreads to multiple lymph nodes, extranodal sites, and spleen, liver, and bone marrow. Single site involvement is more common in certain subtypes of non-Hodgkin lymphoma.

**Clinical Pearl:**
Understanding the clinicopathological characteristics of Hodgkin lymphoma is essential for making an accurate diagnosis and selecting the appropriate treatment plan. Awareness of the disease's age distribution, presentation, and site of involvement helps medical professionals in making a proper clinical assessment. This knowledge is beneficial in formulating a differential diagnosis, considering the patient's overall health status, and planning the most effective treatment strategy for the patient.