**Core Concept:** The Reed-Sternberg (RS) cells are large, histiocytoid cells present in Hodgkin's lymphoma (HL). There are two main subtypes of HL: classical Hodgkin lymphoma (cHL) and nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL).

**Why the Correct Answer is Right:** Lacunar type of Reed-Sternberg cells are seen in nodular sclerosis subtype of classical Hodgkin lymphoma (cHL). In cHL, RS cells form a nodular pattern within the affected lymph nodes, surrounded by a surrounding rim of reactive cells (Langhans giant cells and T cells).

**Why Each Wrong Option is Incorrect:**

A. Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) typically exhibits a mixed cellularity pattern and has a different morphology. RS cells are of lymphocytic origin in NLPHL.

B. Lymphocyte-rich classical Hodgkin lymphoma (LR-cHL) is characterized by a predominantly lymphocytic infiltrate and lacks the characteristic nodular pattern seen in nodular sclerosis (NS) subtype.

C. In the mixed cellularity subtype of cHL, RS cells are also present but the main feature is the mixed cellular infiltrate, not the lacunar pattern.

D. In the lymphocyte-depleted subtype of cHL, RS cells are rare, and the infiltrate is predominantly composed of small lymphocytes and histiocytes. The lacunar pattern is not a prominent feature.

**Clinical Pearl:** The lacunar pattern is a distinctive feature of nodular sclerosis subtype of classical Hodgkin lymphoma (cHL), which is the most common subtype of cHL. This pattern helps differentiate it from other subtypes, such as nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) and lymphocyte-rich Hodgkin lymphoma (LR-cHL), both of which have distinct morphological features.

**Correct Answer:** .