Villous adenoma

WikiDoc Resources for Villous adenoma
Articles
Most recent articles on Villous adenoma Most cited articles on Villous adenoma Review articles on Villous adenoma Articles on Villous adenoma in N Eng J Med, Lancet, BMJ
Media
Powerpoint slides on Villous adenoma Images of Villous adenoma Photos of Villous adenoma Podcasts & MP3s on Villous adenoma Videos on Villous adenoma
Evidence Based Medicine
Cochrane Collaboration on Villous adenoma Bandolier on Villous adenoma TRIP on Villous adenoma
Clinical Trials
Ongoing Trials on Villous adenoma at Clinical Trials.gov Trial results on Villous adenoma Clinical Trials on Villous adenoma at Google
Guidelines / Policies / Govt
US National Guidelines Clearinghouse on Villous adenoma NICE Guidance on Villous adenoma NHS PRODIGY Guidance FDA on Villous adenoma CDC on Villous adenoma
Books
Books on Villous adenoma
News
Villous adenoma in the news Be alerted to news on Villous adenoma News trends on Villous adenoma
Commentary
Blogs on Villous adenoma
Definitions
Definitions of Villous adenoma
Patient Resources / Community
Patient resources on Villous adenoma Discussion groups on Villous adenoma Patient Handouts on Villous adenoma Directions to Hospitals Treating Villous adenoma Risk calculators and risk factors for Villous adenoma
Healthcare Provider Resources
Symptoms of Villous adenoma Causes & Risk Factors for Villous adenoma Diagnostic studies for Villous adenoma Treatment of Villous adenoma
Continuing Medical Education (CME)
CME Programs on Villous adenoma
International
Villous adenoma en Espanol Villous adenoma en Francais
Business
Villous adenoma in the Marketplace Patents on Villous adenoma
Experimental / Informatics
List of terms related to Villous adenoma

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

Synonyms and keywords: Adenomatous polyps; VA; TVA

Overview

Villous adenoma (also known as adenomatous polyp) is a type of polyp that grows in the gastrointestinal tract and commonly in the colon. Villous adenoma may result in malignant (cancerous) transformation. Villous adenoma was first discovered by Helwig in 1946. According to the World Health Organization, villous adenoma may be classified into tubular, tubulovillous, and villous (most common) subtypes. Villous adenoma arises from epithelial tissue, which is normally part of the lining of the colon. The estimated risk of malignant transformation among villous adenomas is between 15% and 25%. Genes associated with the development of villous adenoma include APC gene, TP53 gene, K-ras gene, and BAT-26 gene. The prevalence of villous adenoma is approximately 3.5 per 100,000 individuals worldwide. The most potent risk factor in the development of villous adenoma are familial syndromes such as Turcot syndrome, juvenile polyposis syndrome, and Cowden disease). Surgical removal is the mainstay of therapy for villous adenoma. Exploratory colonoscopy and cautery snare is the most common approach to the diagnosis and treatment of villous adenoma. Effective measures for the primary prevention of villous adenoma include periodic screening of patients with family history of familial adenomatous polyposis. According to the guidelines established by the American Cancer Society, individuals who reach the age of 50 should undergo an occult blood test yearly.

Historical Perspective

Villous adenoma was first discovered by Helwig in 1946.

Classification

Villous adenoma may be classified according to the World Health Organization into 3 groups:

• Tubular
• Tubulovillous
• Villous (most common)

Pathophysiology

Pathogenesis

The pathogenesis of villous adenoma is characterized by overgrowth of epithelial tissue with glandular characteristics.

Genetics

Genes associated with the development of villous adenoma include:

• APC gene
• TP53 gene
• KRAS gene
• BAT-26 gene

Gross Pathology

On gross pathology, characteristic findings of villous adenoma include:

• Polypoid or sessile mass
• Cauliflower-like in appearance

Microscopic Pathology

On microscopic histopathological analysis, characteristic findings of villous adenoma include:

• Nuclear changes at the surface of the mucosa
• Cigar-shaped (elongated) nucleus (length:width > 3:1) with nuclear hyperchromasia
• Large round nuclei
• Nuclear crowding
• Positive Ki-67

Causes

Villous adenomas are commonly idiopathic. The most common known cause of villous adenoma is familial adenomatous polyposis.

Differentiating Villous Adenoma from Other Diseases

Villous adenoma must be differentiated from other diseases that cause abnormal growth of tissue projecting from a mucous membrane such as:

• Colorectal cancer
• Inflammatory fibroid polyp

Epidemiology and Demographics

Prevalence

The prevalence of villous adenoma is approximately 3.5 per 100,000 individuals worldwide. The prevalence of adenomas increases with age.

Age

Patients of all age groups may develop villous adenoma.

Gender

Males are more commonly affected with villous adenoma than females.

Race

Villous adenoma more commonly affects caucasians.

Risk Factors

Common risk factors in the development of villous adenoma include:

• Familial adenomatous polyposis
• Peutz–Jeghers syndrome
• Turcot syndrome
• Juvenile polyposis syndrome
• Cowden disease
• Bannayan–Riley–Ruvalcaba syndrome (Bannayan-Zonana syndrome)
• Gardner's syndrome

Natural History, Complications and Prognosis

Natural History

The majority of patients with villous adenoma remain asymptomatic for years. Early clinical features may include flatulence, bloating, and abdominal pain. If left untreated, patients with villous adenoma may progress to develop colorectal cancer.

Complications

Common complications of villous adenoma include:

• Bleeding
• Obstruction
• Bowel torsion

Prognosis

The prognosis of villous adenoma is generally good and the 5-year mortality is approximately 89%. Prognosis becomes poorer with malignant transformation of the lesion. The estimated risk of malignant transformation of villous adenoma is from 15% to 20%.

Diagnosis

Symptoms

Villous adenoma is usually asymptomatic. Villous adenoma symptoms are often non-specific. Symptoms of villous adenoma may include:

• Flatulence
• Abdominal pain
• Constipation
• Diarrhea
• Cramping

Physical Examination

Patients with villous adenoma commonly appear well. Physical examination findings are often non-specific. Physical examination may demonstrate:

• Rectal bleeding
• Rectal mass
• Pencil-thin stools

Laboratory Findings

There are no specific laboratory findings associated with villous adenoma. In some cases, patients with villous adenoma may demonstrate positive fecal occult blood test or hypokalemia.

Imaging and Diagnostic Findings

Colonoscopy is the diagnostic modality of choice for villous adenoma. On colonoscopy, characteristic findings of villous adenoma include:

• A sessile polyp
• Size can range from 0.5 cm to 5 cm

Other imaging studies include:

• CT colonography
• Video capsule endoscopy (less specific)

Treatment

Medical Therapy

There is no medical treatment for villous adenoma; the mainstay of therapy is surgical removal.

Surgery

Surgical removal is the mainstay of therapy for villous adenoma. Colonoscopy is both diagnostic and therapeutic. Cautery snare in conjunction with exploratory colonoscopy is the most common approach to both the diagnosis and treatment of villous adenoma.

Prevention

Effective measures for the primary prevention of villous adenoma include periodic screening for patients with family history of familial adenomatous polyposis. According to the guidelines established by the American Cancer Society, individuals who reach the age of 50 should perform an occult blood test yearly, a colonoscopy every 10 years, or a flexible sigmoidoscopy every 3 to 5 years. Once diagnosed and successfully treated, patients with villous adenoma are followed-up every 12 to 24 months.