## Extranodal NHL: Most Common Sites **Key Point:** The gastrointestinal (GI) tract is the most common site of extranodal involvement in non-Hodgkin lymphomas, accounting for 5–20% of all NHL presentations and up to 40% of extranodal NHLs. ## Frequency of Extranodal Sites | Site | Frequency | Notable Type | |------|-----------|---------------| | **Gastrointestinal tract** | 5–20% of all NHLs; 40% of extranodal | MALT lymphoma (stomach), EATL | | **Bone marrow** | ~25% at diagnosis (often occult) | SLL/CLL, follicular lymphoma | | **Liver** | 5–10% | Hepatosplenic T-cell lymphoma | | **CNS** | 2–5% (higher in immunocompromised) | PCNSL, lymphoblastic | | **Bone** | 2–5% | Primary bone lymphoma (rare) | | **Testis** | 1–2% | Primary testicular lymphoma | **High-Yield:** GI involvement is most *clinically apparent* because: - Presents with abdominal pain, obstruction, bleeding, or perforation - Often requires endoscopy and biopsy for diagnosis - MALT lymphoma of stomach is strongly associated with *H. pylori* infection ## Clinical Pearl: Bone Marrow Involvement **Warning:** Bone marrow involvement is actually present in ~25% of NHL cases at diagnosis but is often *occult* (found only on staging marrow biopsy). However, GI tract is the most *clinically significant* and most *frequently diagnosed* extranodal site because it causes symptoms and is accessible to endoscopy. ## GI Lymphomas: Subtypes 1. **MALT lymphoma** (stomach) — associated with *H. pylori*; may regress with eradication 2. **Enteropathy-associated T-cell lymphoma (EATL)** — associated with celiac disease 3. **Burkitt lymphoma** — can present with bowel obstruction or perforation 4. **DLBCL** — can involve any GI segment **Mnemonic: "GI is the Gateway"** — Gastrointestinal tract is the gateway for extranodal NHL.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.