A 62-year-old Indian woman with a history of pernicious anemia (intrinsic factor antibodies positive) and chronic atrophic gastritis presents with a 3-month history of persistent epigastric pain and vomiting. Upper endoscopy reveals a 4 cm polypoid lesion in the gastric fundus with areas of ulceration. Histopathology shows well-differentiated adenocarcinoma with intact glandular structures and intestinal-type epithelium. There is no evidence of signet-ring cells. Staging CT shows no distant metastases but involvement of perigastric lymph nodes. Which of the following best describes the carcinogenic sequence in this patient?

Explanation

## Carcinogenic Sequence in Pernicious Anemia–Associated Gastric Cancer ### The Correa Cascade (Modified for Pernicious Anemia) **Key Point:** The Correa cascade describes the stepwise progression from normal mucosa to gastric cancer. In pernicious anemia, the sequence is: ```mermaid flowchart TD A[Pernicious Anemia<br/>Intrinsic Factor Antibodies]:::outcome --> B[Vitamin B12 Deficiency<br/>Impaired DNA synthesis & repair]:::outcome B --> C[Chronic Atrophic Gastritis<br/>Autoimmune destruction of parietal cells]:::outcome C --> D[Loss of HCl & Intrinsic Factor<br/>Achlorhydria]:::outcome D --> E[Intestinal Metaplasia<br/>Replacement of gastric mucosa]:::outcome E --> F[Low-Grade Dysplasia]:::outcome F --> G[High-Grade Dysplasia]:::outcome G --> H[Intestinal-Type Adenocarcinoma<br/>Well-formed glands]:::action H --> I[Regional Lymph Node Involvement<br/>Stage IB-II]:::outcome ``` ### Histological Features in This Patient | Feature | Finding | Significance | |---------|---------|---------------| | **Histology** | Well-differentiated adenocarcinoma | Intestinal type | | **Glandular structures** | Intact, organized | Not signet-ring cell (diffuse) | | **Epithelium** | Intestinal-type | Arises from metaplastic mucosa | | **Location** | Fundus | Site of parietal cell loss | | **Precursor lesion** | Atrophic gastritis + intestinal metaplasia | Correa cascade | **High-Yield:** Pernicious anemia → atrophic gastritis → intestinal metaplasia → dysplasia → intestinal-type gastric cancer. This is the classic teaching sequence and accounts for ~10% of gastric cancers in high-risk populations. ### Why Pernicious Anemia Increases Cancer Risk 1. **Vitamin B12 deficiency** impairs DNA synthesis and repair → increased mutagenesis 2. **Autoimmune destruction of parietal cells** → loss of HCl and intrinsic factor 3. **Achlorhydria** allows bacterial overgrowth and nitrosamine production 4. **Intestinal metaplasia** is a precancerous lesion with altered differentiation 5. **Dysplasia** develops over years to decades 6. **Adenocarcinoma** emerges, typically intestinal type (well-formed glands) **Clinical Pearl:** Patients with pernicious anemia have a 2–3-fold increased risk of gastric cancer. Screening with endoscopy is recommended in some high-risk populations, especially those with extensive atrophic gastritis and intestinal metaplasia. ### Distinction from H. pylori–Associated Gastric Cancer **Warning:** Do NOT confuse pernicious anemia–associated cancer with H. pylori–associated cancer. While both involve atrophic gastritis and intestinal metaplasia, the initiating mechanism differs: - **Pernicious anemia:** Autoimmune (intrinsic factor antibodies) → B12 deficiency - **H. pylori:** Bacterial infection → chronic inflammation → atrophic gastritis Both can lead to intestinal-type cancer, but pernicious anemia is specifically tied to autoimmune parietal cell destruction. **Mnemonic: PICA = Pernicious anemia → Intestinal metaplasia → Cancer → Atrophic gastritis (precedes)** [cite:Robbins 10e Ch 17]