**Question:** Reed-Steinberg cells of Hodgkin's disease positive for CD15 & CD30 are seen in all types EXCEPT:

A. Nodular Sclerosis
B. Lymphocyte-rich
C. Mixed cellularity
D. Pure red cell aplasia

**Correct Answer:**

**Core Concept:** Hodgkin's disease is a type of lymphoma characterized by the presence of Reed-Sternberg (or Reed-Steinberg) cells. In this question, we are discussing the CD15 and CD30 expression on these cells.

**Why the Correct Answer is Right:**

Reed-Sternberg (or Reed-Steinberg) cells in Hodgkin's disease express CD15 and CD30 antigens, which are markers for these cells. These cells are a hallmark of Hodgkin's disease. In terms of histological subtypes, CD15 and CD30 positivity is seen in all types of Hodgkin's disease except for Pure Red Cell Aplasia (PRCA).

**Why Each Wrong Option is Incorrect:**

A. Nodular Sclerosis: Reed-Sternberg cells express CD15 and CD30 antigens, making this option incorrect as it includes the presence of these cell types.
B. Lymphocyte-rich: Although lymphocytes are a component of this subtype, Reed-Sternberg cells are present, rendering this option incorrect.
C. Mixed Cellularity: Reed-Sternberg cells express CD15 and CD30 antigens, making this option incorrect as it includes the presence of these cell types.
D. Pure Red Cell Aplasia: Reed-Sternberg cells are not present in PRCA, which is a disorder characterized by reduced or absent red blood cell production.

**Clinical Pearl:** Understanding the characteristics of Reed-Sternberg cells and their marker expression is crucial for diagnosing and differentiating Hodgkin's disease from other lymphoproliferative disorders. A positive CD15 and CD30 expression in a given lymphoproliferative disorder should raise suspicion for Hodgkin's disease, but the presence of these cells in Pure Red Cell Aplasia (PRCA) rules out this diagnosis. PRCA is a distinct clinical entity characterized by reduced or absent red blood cell production, which is distinct from the lymphoproliferative nature of Hodgkin's disease.

**Why Each Wrong Option is Incorrect:**

A. Nodular Sclerosis: Reed-Sternberg cells express CD15 and CD30 antigens, making this option incorrect as it includes the presence of these cell types.
B. Lymphocyte-rich: Although lymphocytes are a component of this subtype, Reed-Sternberg cells are present, rendering this option incorrect as well.
C. Mixed Cellularity: Reed-Sternberg cells express CD15 and CD30 antigens, making this option incorrect as it includes the presence of these cell types.

**Core Concept:** The understanding of Reed-Sternberg cells and their marker expression helps in diagnosing