What actions should be taken if histology results of appendicitis show a low-grade appendiceal neoplasm?

Management of Low-Grade Appendiceal Neoplasm

For patients with low-grade appendiceal neoplasm discovered on histology after appendectomy, management should be based on tumor size, location, and histological features, with right hemicolectomy indicated for tumors ≥2 cm or those with high-risk features. 1

Decision Algorithm Based on Tumor Size and Features

For Well-Differentiated Tumors <2 cm:

• Simple appendectomy is sufficient for tumors <1 cm confined to the appendix with no adverse features, as this is likely curative 1
• No extended follow-up is necessary for completely resected lesions <1 cm 1
• Further resection (right hemicolectomy) should be considered if the tumor:
  • Breaches the serosal surface 1
  • Invades the mesoappendix by more than 3 mm 1
  • Is located at the base of the appendix 1

For Tumors ≥2 cm:

• Right hemicolectomy is indicated, even without obvious malignant features 1
• This recommendation is based on higher risk of lymph node metastases and locoregional spread 1

For Goblet Cell Appendiceal Tumors:

• Right hemicolectomy is always required regardless of size due to their more aggressive behavior 1
• These tumors should be managed according to colon cancer protocols rather than typical neuroendocrine tumor protocols 1, 2
• In women, consider bilateral oophorectomy due to increased risk of pelvic peritoneal metastases 1

Staging and Additional Workup

• For patients with incomplete resection or tumors ≥2 cm:

  • Perform abdominal/pelvic CT or MRI to rule out distant disease 1
  • If no distant disease is identified, proceed with right hemicolectomy 1

• For low-grade appendiceal mucinous neoplasms (LAMN):

  • Assess for presence of acellular mucin on the serosa and surgical margins as these are risk factors for pseudomyxoma peritonei 3
  • If appendix perforation is present, evaluate for peritoneal spread 3

Surveillance Recommendations

• For tumors <2 cm with complete resection and no adverse features:

  • Follow-up examinations as clinically indicated 2
  • Some institutions recommend examination at 1 year post-appendectomy with decreasing frequency thereafter 2

• For larger tumors or those with adverse features:

  • Follow-up every 3-12 months for up to 10 years 1
  • Consider chromogranin A as a tumor marker for neuroendocrine tumors 2
  • Perform multiphasic CT or MRI (abdominal/pelvic) during follow-up 1

Important Considerations and Pitfalls

• Avoid unnecessary right hemicolectomy for small (<1 cm) well-differentiated tumors at the tip of the appendix without adverse features 1, 4
• Be aware that even small tumors with certain histological features (invasion, location at base) may require more aggressive management 1
• For LAMN, a detailed pathological assessment is crucial as T stage, appendix perforation, and presence of acellular mucin on the serosa are important prognostic factors 3, 5
• Referral to centers with experience in peritoneal surface malignancies should be considered for complex cases, especially those with evidence of peritoneal spread 6