Endoscopic characterization of synchronous esophageal, gastric, and colorectal involvement in multisystem Langerhans cell histiocytosis

The endoscopic characterization of synchronous esophageal, gastric, and colorectal involvement in multisystem Langerhans cell histiocytosis (LCH) involves identifying specific patterns and features across the gastrointestinal (GI) tract. This is particularly important as GI involvement in adult-onset LCH is rare and often under-recognized. Below is a detailed description of the endoscopic findings and their implications:

### 1. **Esophageal Involvement**

• **Appearance of Lesions**: The esophageal lesions in LCH typically present as raised plaques with central depressions. These plaques may also exhibit:
• Radial telangiectasia (dilated blood vessels radiating outward).
• Barnacle-like satellite nodules surrounding the primary lesion.
• **Endoscopic Recognition**: These findings are distinct and can serve as a clue to the diagnosis, especially when combined with systemic manifestations of LCH.
• **Challenges**: Superficial biopsies may not always capture diagnostic tissue due to the subepithelial nature of the lesions.

### 2. **Gastric Involvement**

• **Lesion Diversity**: Gastric lesions in LCH can show a variety of morphologies, including:
• Ulcerative defects with visible surface erosion.
• Firm submucosal protrusions that may appear as masses beneath the mucosa.
• **Diagnostic Difficulty**: The submucosal predominance of gastric lesions often complicates diagnosis, as the overlying mucosa may remain intact or only superficially eroded.
• **Novel Endoscopic Sign**: The “mucosal fragmentation sign” has been described during endoscopic resection. This sign indicates fragile mucosa overlying tumor tissue, which fragments easily due to outward pressure from the submucosal tumor.

### 3. **Colorectal Involvement**

• **Distribution and Morphology**: In the colon, LCH lesions often appear as clustered submucosal masses. These are particularly prominent in:
• The ileocecal region.
• The sigmoid colon.
• **Endoscopic Features**: The lesions are primarily subepithelial, with intact or minimally altered mucosa, which can obscure their detection during routine endoscopy.
• **Clinical Implications**: Colorectal lesions may mimic other conditions like carcinoma or lymphoma, increasing the risk of misdiagnosis.

### 4. **Submucosal Predominance**

• Across the esophagus, stomach, and colon, a key feature of GI LCH lesions is their submucosal location. This makes superficial biopsies less effective, and deep biopsies are often required to retrieve diagnostic tissue.
• **Histologic Confirmation**: Once tissue is obtained, the diagnosis is confirmed by identifying Langerhans cells that are positive for markers such as CD1a, S100, and Langerin.

### 5. **Endoscopic Challenges and Diagnostic Strategies**

• **Imaging Limitations**: Conventional imaging and even PET scans may fail to detect these mucosal or submucosal lesions, emphasizing the critical role of endoscopy.
• **Biopsy Technique**: Deep biopsies are essential for accurate diagnosis. The “mucosal fragmentation sign” can guide endoscopists in identifying areas for targeted sampling.
• **Differential Diagnosis**: GI LCH lesions may mimic other diseases, including carcinoma, lymphoma, or inflammatory bowel disease. Recognizing the characteristic endoscopic patterns is key to avoiding misdiagnosis.

### 6. **Asymptomatic Involvement**

• Extensive GI involvement can occur even in patients without digestive symptoms. This underscores the importance of proactive endoscopic evaluation in patients with confirmed LCH, regardless of symptomatology.

### 7. **Clinical Recommendations**

• Patients with multisystem LCH should undergo a systematic and comprehensive endoscopic evaluation of the GI tract, even if they are asymptomatic.
• Awareness of the specific endoscopic patterns associated with LCH can facilitate earlier and more accurate diagnosis, improving patient outcomes.

### Summary

Endoscopic findings in synchronous esophageal, gastric, and colorectal involvement in LCH are distinct and can include raised plaques, submucosal protrusions, ulcerations, and clustered masses. The submucosal predominance of these lesions often necessitates deep biopsies for diagnosis. Recognizing characteristic endoscopic patterns, such as radial telangiectasia, barnacle-like nodules, and the mucosal fragmentation sign, is crucial for identifying GI LCH. Proactive endoscopic evaluation is recommended in all patients with confirmed LCH to detect potential GI involvement, even in the absence of symptoms.