Villous Adenoma

Published on 13/07/2015 by admin

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Last modified 22/04/2025

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Accounts for 5-15% of colonic adenomas

IMAGING

• Polypoid lesion with nodular or frond-like surface on BE or CT colonography

• Location: Rectosigmoid > cecum > ascending colon > stomach > duodenum

• Villous adenoma is 1 histological type of adenomatous polyps (true neoplasms)

• Risk of cancer is related to tumor size, location, and proportion of villous change in adenoma

• Greater risk of carcinoma in villous tumors of stomach and duodenum than colon

Stomach: Carcinoma in 50% of lesions 2-4 cm and in 80% of lesions > 4 cm in size

Colon: Invasive carcinoma in up to 45% of cases

• CT: Large villous adenoma

Low-attenuation, minimally enhancing, irregular polypoid mass

Corrugated, feathery appearance due to trapping of enteric contrast

• Transrectal US; plus CT or MR for staging

TOP DIFFERENTIAL DIAGNOSES

• Colon carcinoma

• Fecal mass

PATHOLOGY

• Malignant potential: Lesions < 1 cm (5%), 1-2 cm (10%), > 2 cm (53%)

CLINICAL ISSUES

• Asymptomatic, diarrhea, pain, rectal bleeding, or melena

• Lesion closer to rectum: More likely to have diarrhea, electrolyte loss (hypokalemia and hyponatremia)

(Left) Graphic shows a polypoid mass in the rectosigmoid colon having a shaggy, nodular surface, sometimes likened to the surface of a cauliflower.

(Left) Graphic shows a polypoid mass in the rectosigmoid colon having a shaggy, nodular surface, sometimes likened to the surface of a cauliflower.

(Right) Single contrast barium enema shows a large rectal mass with a frond-like surface. Note the absence of a colonic obstruction, a typical feature of this soft and compressible tumor.

(Right) Single contrast barium enema shows a large rectal mass with a frond-like surface. Note the absence of a colonic obstruction, a typical feature of this soft and compressible tumor.

(Left) This 70-year-old man complained of frequent passage of watery stool, but had no symptoms of bowel obstruction. CT shows a large mass that fills the rectum. Note large vessels within and draining the mass.

(Left) This 70-year-old man complained of frequent passage of watery stool, but had no symptoms of bowel obstruction. CT shows a large mass that fills the rectum. Note large vessels within and draining the mass.

(Right) Coronal CT reformation in the same case shows the huge size of the mass , but no definite signs of invasion through the rectal wall and no metastases. The resected villous adenoma had foci of frank carcinoma.

(Right) Coronal CT reformation in the same case shows the huge size of the mass , but no definite signs of invasion through the rectal wall and no metastases. The resected villous adenoma had foci of frank carcinoma.

TERMINOLOGY

Synonyms

• Villous tumor

Definitions

• Adenomatous polyp that contains predominantly villous (“shaggy” surface) elements

IMAGING

General Features

• Best diagnostic clue

Polypoid lesion with nodular or frond-like surface on barium enema or CT colonography

• Location

Rectosigmoid > cecum > ascending colon > stomach > duodenum

• Size

Range from < 1 to > 10 cm in diameter

Giant villous tumor: 10-15 cm

• Morphology

Cauliflower-like sessile growth with broad base or flat “carpet” lesion

• Other general features

Villous adenoma is 1 histological type of adenomatous polyps (true neoplasms)

– Tubular adenoma: > 80% of neoplastic polyps

– Villous adenoma: 5-15% of colonic polyps, villous morphology in > 75% of lesion

– Tubulovillous adenoma: 5-15% of all colonic polyps

As adenoma increases in size, degree of villous change usually increases

Risk of cancer is related to size, location, and proportion of villous change in adenoma

Greater risk of carcinoma in villous tumors of stomach and duodenum than colon

– Stomach: Carcinoma in 50% of lesions 2-4 cm and in 80% of lesions > 4 cm

– Duodenum: Carcinoma in 30-60% of villous tumors > 4 cm

– Colon: Carcinoma in situ in 10% and invasive carcinoma in up to 45% of cases

Radiographic Findings

• Fluoroscopic-guided double contrast barium enema

2 types of villous adenomas

– Polypoid mass

– “Carpet” lesion

Polypoid mass

– May look cauliflower-like within colon

– Nodular, “lace,” or “soap bubble” pattern

– Due to trapping of barium between frond-like projections (interstices)

– Malignant transformation in bulky adenoma: Annular lesion with shelf-like, overhanging borders

“Carpet” lesion

– Flat, lobulated lesion

– Localized or extensive

Localized “carpet” lesion: Subtle alteration in surface texture

Extensive “carpet” lesion: Involves large area of colon, encircling lumen

– En face: Fine nodular, reticular pattern with sharply demarcated border

– Profile: Irregular contour in contrast to smooth, fine contour of adjacent normal bowel

Malignant transformation in “carpet” lesion (↑ risk)

– Radiolucent nodules surrounded by barium-filled grooves (produce fine nodular or reticular pattern)

– Polypoid carcinoma with surrounding mucosal change represents underlying adenoma

– Seen in rectum, cecum, ascending colon, stomach, and duodenum

CT Findings

• Large villous adenoma

Low-attenuation, minimally enhancing, irregular polypoid mass

Convolutional gyral enhancement pattern

Corrugated, feathery appearance due to trapping of enteric contrast within interstices of villous adenoma

• CT colonography

Appearance of villous tumors similar to that seen on barium enema

CTC shows more polyps than barium enema

MR Findings

• Large villous adenoma

T1WI: Low signal intensity mass with multiple frond-like projections and central cord-like structure

T2WI: Frond-like projections will be more prominent

• Villous adenoma with more mucin-producing cells

Short T1 and long T2 times

Adenoma appears hyperintense on both T1- and T2WI

Ultrasonographic Findings

• Transrectal sonography

Determines depth of invasion into colonic wall by adenoma

Imaging Recommendations

• CT colonography (or barium enema) for screening

• Transrectal US; plus CT or MR for staging

DIFFERENTIAL DIAGNOSIS

Colon Carcinoma

• Barium enema findings

Early cancer: Sessile (plaque-like) lesion

– Typical early colon cancer

– Flat, protruding lesion with broad base and little elevation of mucosa (in profile view)

Early cancer: Pedunculated lesion

– Short and thick polyp stalk

– Irregular or lobulated head of polyp

Advanced cancer: Polypoid lesion (large)

– Dependent wall: Filling defect in barium pool

– Nondependent wall: Surface of tumor is etched in white

Sessile and pedunculated polypoid cancers may be indistinguishable from villous adenoma

Advanced cancer: Semiannular (“saddle”) lesion

Advanced cancer: Annular (“apple core”) lesion

– Circumferential narrowing of bowel

– Shelf-like, overhanging borders (mucosal destruction)

• CT findings

Asymmetric mural thickening ± irregular surface

Extracolonic tumor extension

– Mass with irregular borders

– Extension from serosa to pericolic fat

– Loss of fat planes: Colon and adjacent muscles

Metastases to regional mesenteric nodes

Metastases to liver

• Diagnosis: Biopsy and histology

Fecal Mass

• Large, irregular colonic fecal impaction

Most common location: Rectum

• Mimics large, cauliflower-like sessile polyp

• May cause bowel obstruction and proximal dilatation

• Usually seen in elderly, sedentary patients

• Diagnosis: Clinical history and colonoscopy

Intramural Benign Tumor, Colonic

• e.g., stromal tumors (leiomyoma, sarcoma, or GIST)

• Leiomyoma

In profile

– Smooth surface, etched in white

– Borders: Right or obtuse angles with adjacent wall

En face

– Seen as filling defect simulating polypoid type of villous adenoma

– Intraluminal surface: Abrupt, well-defined borders

• Leiomyosarcoma

Bulky stromal tumors most frequently seen in rectum

Broad-based mass simulating large villous adenoma

Large tumors show ulceration or cavitation

CT shows pericolonic extension (large extraluminal mass), liver, and peritoneal metastases

• Hypervascular on angiography

• Diagnosis: Biopsy

PATHOLOGY

General Features

• Etiology

Villous adenoma or tumor

– Family history, idiopathic inflammatory disease

– Malignant potential: Lesions < 1 cm (5%), 1-2 cm (10%), > 2 cm (53%)

Gross Pathologic & Surgical Features

• Usually sessile

May be polypoid, broad, flat, or carpet-like lesion

Gray-tan lesion

• May have short, broad stalk and focal areas of hemorrhage or ulceration

Microscopic Features

• Frond-like papillary projections of adenomatous epithelium

• ± well-differentiated areas

• Carcinoma in situ, invasive cancer

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

Asymptomatic, diarrhea, pain, rectal bleeding, or melena

Lesion closer to rectum: More likely to have diarrhea, electrolyte loss (hypokalemia)

• Lab data

Guaiac positive stool

Iron deficiency anemia

Decreased serum protein, K+, Na+

– “McKittrick-Wheelock syndrome” if caused by rectal tumor, usually villous adenoma

± increased direct bilirubin levels (due to obstruction of ampulla of Vater by adenoma)

• Diagnosis: Endoscopy, biopsy, and histology

Demographics

• Age

60-70 years or older

• Gender

M = F

Natural History & Prognosis

• Complications

Malignant transformation or invasion; hemorrhage

• Prognosis

Good: After removal of benign and carcinoma in situ adenoma

Poor: Invasive carcinoma

Treatment

• Colonoscopic, endoscopic, or surgical resection

DIAGNOSTIC CHECKLIST

Consider

• Check for family history of colonic polyps and evaluate entire colon for synchronous lesions

Image Interpretation Pearls

• Cauliflower-like sessile mass with broad base or “carpet” lesion with reticular or “soap bubble” surface pattern

• Luminal obstruction is a late finding

(Left) Barium pool image from a double contrast barium enema shows a cauliflower-like mass in the cecum, a typical appearance of a villous adenoma.

(Left) Barium pool image from a double contrast barium enema shows a cauliflower-like mass in the cecum, a typical appearance of a villous adenoma.

(Right) Spot film from an air contrast barium enema in the same patient shows the villous adenoma coated with barium and outlined by air on this view.

(Right) Spot film from an air contrast barium enema in the same patient shows the villous adenoma coated with barium and outlined by air on this view.

(Left) Axial CECT in an 85-year-old woman with acute abdominal pain shows a transverse colo-colonic intussusception due to a large lead point mass .

(Left) Axial CECT in an 85-year-old woman with acute abdominal pain shows a transverse colo-colonic intussusception due to a large lead point mass .

(Right) More caudal CT section in the same patient shows the colonic mass , a villous adenoma, as the lead point of the colonic intussusception.

(Right) More caudal CT section in the same patient shows the colonic mass , a villous adenoma, as the lead point of the colonic intussusception.

(Left) Axial CECT in the same patient just proximal to the intussusception shows another smaller, lobulated, enhancing mass within the ascending colon that proved to be a 2nd villous adenoma.

(Left) Axial CECT in the same patient just proximal to the intussusception shows another smaller, lobulated, enhancing mass within the ascending colon that proved to be a 2nd villous adenoma.

(Right) Single contrast BE in the same patient demonstrates temporary reduction of the intussusception, with the 2 villous adenomas seen as masses with irregular surface contours within the barium pool. A right hemicolectomy and histopathology confirmed the diagnosis.

(Right) Single contrast BE in the same patient demonstrates temporary reduction of the intussusception, with the 2 villous adenomas seen as masses with irregular surface contours within the barium pool. A right hemicolectomy and histopathology confirmed the diagnosis.

Single contrast BE shows a polypoid mass in the rectosigmoid colon with a very nodular surface. Barium within the rectum is diluted by mucus secreted by the tumor.

Single contrast BE shows a polypoid mass in the rectosigmoid colon with a very nodular surface. Barium within the rectum is diluted by mucus secreted by the tumor.

Axial CECT shows a large mass that fills the rectosigmoid colon with dilated stool-filled colon, noted more proximally.

Axial CECT shows a large polypoid mass within the rectum.

Axial CECT shows a large polypoid mass within the rectum.

Air contrast BE shows a rectal mass with a nodular surface that fills, but does not obstruct, the rectal lumen.

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