What is the recommended staging and treatment approach for a patient with signet ring cell gastric carcinoma?

Staging for Signet Ring Cell Gastric Carcinoma

Signet ring cell gastric carcinoma should be staged using the identical TNM staging system and diagnostic workup as other gastric adenocarcinomas, with no modifications to the staging approach based on histology alone. 1

Mandatory Staging Investigations

The complete staging workup must include:

• Physical examination with assessment for ascites, palpable masses, and Virchow's node 1
• Complete blood count to detect iron-deficiency anemia 1
• Liver and renal function tests to determine treatment eligibility 1
• Upper endoscopy with multiple biopsies for histological confirmation and Lauren classification 1
• Contrast-enhanced CT of thorax, abdomen, and pelvis (plain CT is inadequate) 1
• Endoscopic ultrasound (EUS) for accurate T and N staging, particularly valuable for determining depth of invasion with 86% sensitivity for distinguishing T1/2 from T3/4 disease 1
• Diagnostic laparoscopy with peritoneal washings for all stage IB-III disease to detect occult peritoneal metastases, which imaging frequently misses 1, 2

TNM Staging Classification

Use the standard AJCC/UICC TNM system without modification for signet ring cell histology 1:

• T stage: Depth of invasion from mucosa (T1a) through serosa (T3) to adjacent structures (T4) 1
• N stage: Number of involved regional lymph nodes (N0 = none, N1 = 1-6, N2 = 7-15, N3 = >15) 1
• M stage: Presence or absence of distant metastases 1

Critical Staging Considerations Specific to Signet Ring Cell Histology

PET imaging has limited utility in signet ring cell carcinoma because these mucinous, diffuse-type tumors frequently show false-negative results, making CT and laparoscopy more reliable 1

Laparoscopy is particularly critical because signet ring cell carcinoma has higher propensity for peritoneal dissemination that CT scanning underdetects 1, 2

Minimum lymph node harvest of 15 nodes is mandatory (optimally ≥25 nodes) for accurate N staging, as inadequate lymph node evaluation leads to understaging and suboptimal treatment planning 1, 3

HER2 Testing Requirements

All gastric and esophagogastric junction adenocarcinomas, including signet ring cell type, must undergo HER2 immunohistochemistry testing to determine eligibility for trastuzumab-based therapy in metastatic disease 1

Stage-Specific Implications for Treatment Planning

For early stage (T1a) signet ring cell carcinoma: Endoscopic resection may be considered if confined to mucosa, well-differentiated, non-ulcerated, ≤2 cm, and no lymphovascular invasion, as early signet ring cell carcinoma shows favorable lymph node metastasis rates (10.7%) compared to advanced stages 2, 4, 5

For stage IB and above: Perioperative chemotherapy followed by surgery is standard, requiring multidisciplinary team evaluation before treatment initiation 1, 2, 3

For clinical stage I disease specifically: Surgery alone is the preferred approach for signet ring cell histology, as preoperative therapy shows worse 5-year survival (71% surgery alone vs 58% perioperative chemotherapy vs 38% neoadjuvant therapy) 6

Common Staging Pitfalls to Avoid

Do not proceed to surgery without laparoscopy in potentially resectable stage IB-III disease, as imaging misses peritoneal metastases in a significant proportion of signet ring cell cases 1, 2

Do not rely on PET scanning for staging signet ring cell carcinoma, as the diffuse, mucinous nature produces false-negative results 1

Do not accept lymph node evaluation with <15 nodes examined, as this leads to systematic understaging 1, 3

Do not assume signet ring cell histology automatically warrants more aggressive preoperative therapy for stage I disease, as this approach worsens survival compared to surgery alone 6