Which feature most reliably distinguishes the nodular sclerosis subtype of classical Hodgkin lymphoma from the lymphocyte-rich subtype?

Explanation

## Nodular Sclerosis vs. Lymphocyte-Rich cHL ### Histological Subtypes of Classical Hodgkin Lymphoma Classical Hodgkin lymphoma is subdivided into four histological subtypes based on morphology and background composition: | Subtype | Frequency | Key Feature | Background | Prognosis | |---------|-----------|-------------|------------|----------| | **Nodular Sclerosis** | 60–70% | **Fibrous bands, nodular fibrosis** | Mixed inflammatory | Good | | **Lymphocyte-Rich** | 5% | Numerous small lymphocytes | Sparse Hodgkin/RS cells | Excellent | | Mixed Cellularity | 15–25% | Numerous Hodgkin/RS cells | Mixed, no fibrosis | Intermediate | | Lymphocyte-Depleted | <5% | Abundant Hodgkin/RS cells | Few lymphocytes | Poor | ### Nodular Sclerosis: Defining Architecture **Key Point:** The nodular sclerosis subtype is defined by the presence of **fibrous bands and nodular fibrosis** that divide the lymph node into nodules. This architectural feature is pathognomonic and is the primary discriminator. **High-Yield:** Nodular sclerosis accounts for 60–70% of all cHL cases and is the most common subtype. It typically presents with mediastinal involvement and supraclavicular lymphadenopathy. ### Lymphocyte-Rich Subtype: Defining Feature **Clinical Pearl:** The lymphocyte-rich subtype is characterized by: - Abundant small lymphocytes (>40% of cellularity) - Sparse Hodgkin and Reed-Sternberg cells - **Absence of fibrous bands and nodular fibrosis** - Better prognosis than nodular sclerosis ### Why Fibrosis is the Discriminator **Mnemonic:** **FIBROSIS = Nodular Sclerosis** - **F**ibrous bands - **I**ncomplete nodular division - **B**ackground mixed inflammation - **R**eed-Sternberg cells (variable) - **O**ften mediastinal - **S**taged higher at presentation - **I**ntermediate prognosis - **S**ubtype most common The lymphocyte-rich subtype lacks this fibrotic architecture entirely. ### EBV Status: Not a Discriminator **Warning:** EBV positivity varies across all cHL subtypes and is not a reliable discriminator between nodular sclerosis and lymphocyte-rich subtypes. [cite:Robbins 10e Ch 13]