Appendix cancer

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2] Faizan Sheraz, M.D. [3]

Synonyms and keywords: Tumors of the appendix; Appendiceal cancer; Cancer of the appendix; Neoplasms of the appendix

Overview

Appendix cancer is a rare malignancy of the vermiform appendix. The most common type of appendix cancer is carcinoid tumor. Appendix cancers often present with peritoneal seeding, resulting in peritoneal carcinomatosis or pseudomyxoma peritonei. Appendix cancer may be classified according to WHO classification into 4 groups: epithelial tumors, non-epithelial tumors, secondary tumors, and hyperplastic (metaplastic) polyp. Common causes of appendix cancer may include hereditary syndromes (eg. familial adenomatous polyposis, hereditary non-polyposis colorectal cancer) and chronic inflammatory diseases (eg. ulcerative colitis, Crohn's disease). The estimated prevalence of appendix cancer is approximately 0.12 cases per 100,000 individuals in the United States. On gross pathology, well-demarcated mass, between 1-5 cm, gray or yellowish color are characteristic findings of appendix cancer. Early clinical features include periodical unspecific abdominal pain, bloating, and nausea. Enhanced CT is the imaging modality of choice for appendix cancer. On CT scan, appendix cancer is characterized by the following findings: soft tissue thickening, wall irregularity, presence of pseudomyxoma peritonei, calcification, and internal septations. Surgery is the mainstay of therapy for appendix cancer. Right hemicolectomy in conjunction with chemotherapy is the most common approach to the treatment of appendix cancer. The prognosis of appendix cancer will depend on tumor histology. However, the overall 5-survival rate of patients with appendix cancer is approximately 51%. Once diagnosed and successfully treated, patients with appendix cancer are followed-up every 3, 12 months. Follow-up testing for appendix cancer include physical examination, medical history, imaging studies, chromogranin testing, and laboratory studies (eg. tumoral biomarkers).

Historical Perspective

• Appendix cancer was first described by Gagne, a French Physician, in 1969.

Classification

• Appendix cancer may be classified according to WHO classification into 4 groups:

• Epithelial tumors
• Non-epithelial tumors
• Secondary tumors
• Hyperplastic (metaplastic) polyp

• The table below summarizes the different types of appendix cancer according to the WHO classification.

WHO histological classification Tumors of the appendix Adapted from WHO/IARC
Epithelial tumors
Adenoma Tubular Villous Tubulovillous Serrated Carcinoma Adenocarcinoma Mucinous adenocarcinoma Signet-ring cell carcinoma Small cell carcinoma Undifferentiated carcinoma Carcinoid (well differentiated endocrine neoplasm) Tubular carcinoid Goblet cell carcinoid (mucinous carcinoid) Mixed carcinoid-adenocarcinoma Others
Non-epithelial tumors
Neuroma Lipoma Leiomyoma Gastrointestinal stromal tumor Leiomyosarcoma Kaposi sarcoma Others
Secondary tumors
Metastasis (eg. Primary of urogenital tract, breast, lung)
Hyperplastic polyp

Pathophysiology

• The pathogenesis of appendix cancer is characterized by an initial epithelial dysplasia, followed by the formation of cystic structures and angiolymphatic invasion. Subsequently, in the advanced stages of appendix cancer, tumor cells detach from the primary tumor mass and gain access to the peritoneal cavity.
• The KRAS gene mutation has been associated with the development of appendix cancer.
• On gross pathology, findings of appendix cancer, include:

• Well-demarcated mass
• Average size between 1 and 5 cm
• Gray or yellowish color
• Deformed appendix

• The image below demonstrates gross pathology of appendix cancer.

• 
  Gross pathology appendix cancer

• On microscopic histopathological analysis findings will depend on the subtype of appendicular cancer.
• Common histopathological findings, may include:

• Cystic structures
• Angiolymphatic invasion

• The images below demonstrate different histopathological findings of appendix cancer.

• 
  Appendiceal carcinoid
• 
  Appendiceal carcinoid
• 
  Appendiceal carcinoid with necrosis
• 
  Carcinoid synaptophysin
• 
  Appendiceal tumor

Causes

• Common causes of appendix cancer may include:
• Chronic inflammatory diseases, such as:

• Ulcerative colitis
• Crohn's disease

• Hereditary syndromes, such as:

• Familial adenomatous polyposis
• Hereditary non-polyposis colorectal cancer

Differentiating Appendix Cancer from Other Diseases

• Appendix cancer must be differentiated from other diseases that cause abdominal pain, nausea, vomiting such as:

• Appendicitis
• Typhlitis
• Infectious terminal ileitis
• Ileocecal enteric duplication cyst

Epidemiology and Demographics

• The estimated prevalence of appendix cancer is approximately 0.12 cases per 100,000 individuals in the United States.
• The estimated prevalence of adenocarcinoma of the appendix is 0.2 cases per 100,000 individuals worldwide.
• Appendiceal neoplasms account for approximately 0.4% of gastrointestinal tumors.

Age

• The median age at diagnosis of patients with appendix cancer is 65 years.
• Appendix cancer is more commonly observed among patients aged 50 to 60 years old.
• Appendix cancer is more commonly observed among adults and elderly patients.

Gender

• Males are more commonly affected with appendix cancer than females.

Race

• There is no racial predilection for appendix cancer.

Risk Factors

• Common risk factors in the development of appendix cancer are family history of cancer, long-standing ulcerative colitis, and chronic inflammatory bowel diseases.

Natural History, Complications and Prognosis

• The majority of patients with appendix cancer may be initially asymptomatic.
• Early clinical features include periodical unspecific abdominal pain, bloating, and nausea.
• If left untreated, the majority of patients with appendix cancer may progress to develop peritoneal carcinomatosis and metastases.
• Common complications of appendix cancer include perforation, peritonitis, and abscess.
• Prognosis will depend on tumor histology. However, the overall 5 year survival rate of patients with appendix cancer is approximately 50%.

Diagnosis

Diagnostic Criteria

• The diagnosis of appendix cancer is made with histopathological evaluation of the following diagnostic criteria:

• Tumor confined to the appendix
• Invasion to the muscularis mucosae
• Presence of metastases
• Spread to the peritoneal cavity

Symptoms

• Symptoms of appendix cancer may include the following:

• Chronic abdominal pain

• Periumbilical
• Right lower quadrant

• Loss of appetite
• Nausea
• Vomiting
• Diarrhea
• Micturition
• Tenesmus
• Indigestion
• Flatulence
• Bowel irregularity

Physical Examination

• Patients with appendix cancer may appear normal, pale or diaphoretic.
• Abdominal examination may be remarkable for:

Palpation

• The abdominal wall is very sensitive to mild palpation
• Rebound tenderness
• Abdominal guarding
• Rovsing's sign
• Psoas sign

Rectal examination

• Tenderness in the rectovesical pouch

Laboratory Findings

• Laboratory findings consistent with the diagnosis of appendix cancer, may include:

• Leukocytosis and a shift to the left in the segmented neutrophils.
• Elevated serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA)
• Elevated c-reactive protein (CRP)

Imaging Findings

• Enhanced CT is the imaging modality of choice for appendix cancer.
• On CT, appendix cancer is characterized by the following findings:

• Soft tissue thickening
• Wall irregularity
• Presence of pseudomyxoma peritonei
• Calcification
• Internal septations
• Periappendiceal fat stranding and intraperitoneal free fluid is nonspecific.

Other Diagnostic Studies

• Appendix cancer may also be diagnosed using the following diagnostic studies:

• Somatostatin scintigraphy with 111-indium-octreotide
• Bone scintigraphy with 99mTc-methylene diphosphonate (99mTcMDP)
• Capsule endoscopy
• Enteroscopy
• Positron emission tomography (PET)

Treatment

Medical Therapy

• The mainstay medical therapy for appendix cancer is supportive care.
• Supportive care for appendix cancer, may include:

• Somatostatin analogs
• Systemic chemotherapy or intraperitoneal chemotherapy
• Interferons
• Loperamide or diphenoxylate (for diarrhea)

Surgery

• Surgery is the mainstay of therapy for appendix cancer.
• Right hemicolectomy in conjunction with chemotherapy is the most common approach to the treatment of appendix cancer.

Prevention

• There are no primary preventive measures available for appendix cancer.
• Once diagnosed and successfully treated, patients with appendix cancer are followed-up every 3, 12 months.
• Follow-up testing for appendix cancer includes physical examination, medical history, imaging studies, chromogranin testing, and laboratory studies (eg. tumoral biomarkers).