AJR 2001; 177:91-93
© American Roentgen Ray Society
CT Appearance of Some Colonic Villous Tumors
Theodore R. Smith1,
Sampson W. Fine2 and
Joan G. Jones2
1
Department of Radiology, J. D. Weiler Hospital of the Albert Einstein College
of Medicine and Montefiore Medical Center, 1825 Eastchester Rd., Bronx, NY
10461.
2
Department of Pathology, J. D. Weiler Hospital of the Albert Einstein College
of Medicine and Montefiore Medical Center, Bronx, NY 10461.
Received December 4, 2000;
accepted after revision January 8, 2001.
Address correspondence to T. R. Smith.
Abstract
OBJECTIVE. A review was made of the CT studies and pathology reports
of four patients with surgically resected colonic villous adenomatous tumors,
two of whom had focal carcinomatous invasion.
CONCLUSION. Two patients had villous tumors with IV
contrast-enhancing convolutional gyral patterns. The other two patients had
tumor masses that showed oral contrast medium collecting in surface
interstices, analogous to findings with barium enemas. One of the latter also
had an unusual cluster of mesenteric vessels adjacent to the lesion.
Introduction
Literature regarding the CT appearances of colonic villous adenomas is
scant. Their appearance on CT has been said to be nonspecific
[1], although one report has
described low attenuation in two tumors that was attributed to their high
mucus content on the luminal aspect of the noncystic-shaped masses; it was
also noted that the tumors may have been obscured by oral contrast medium
[2]. The four patients on whom
we report had microscopically proven villous adenomatous lesions with CT
features that, to our knowledge, have not been described previously. The
tumors in two patients showed an unusual IV contrast-enhancing pattern that
produced variegated density in the lesions, conveying a gyral pattern. The
other two patients had villous adenomas that, on CT images, showed oral
contrast medium partially coating the surface interstices, giving a corrugated
or feathery appearance such as that seen in barium enema studies of villous
lesions.
Materials and Methods
The findings of the CT and, when available, barium enema studies of four
patients with villous colonic lesions (age range, 76-83 years, mean age, 79
years) were reviewed as well as the results of the gross and microscopic
pathology reports. All lesions were surgically resected. Patients presented
with various histories of symptoms they had experienced for periods ranging
from 2 weeks to 3 months. These symptoms included guaiac-positive stool (one
patient), rectal bleeding (one patient), and melena (one patient). One tumor
was identified serendipitously at CT in a patient with a history of uterine
carcinoma. Clinical examinations were generally noncontributory, except in the
case of one patient who had a rectal lesion that was digitally palpated.
Abdominal CT was performed on three patients with helical CT (HiSpeedCT/i;
General Electric Medical Systems, Milwaukee, WI) at 7-mm sections and a pitch
of 1 or 1.5. The abdominal CT on the remaining patient was performed at 10-mm
sections (CT 9800; General Electric Medical Systems) (Fig.
1A,1B).
For IV contrast medium, iohexol (Omnipaque 300; Nycomed, New York, NY) was
given (150 mL at 2 mL/sec) at a scan delay of 40 sec. For oral contrast
medium, diatrizoate meglumine 3% (Gastrograffin; Mallinkrodt Medical, St.
Louis, MO) was administered.
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Fig. 1B. —11.5 x 6.0 cm villous adenoma of cecum (cecal
malrotation) in 77-year-old man. Image obtained using barium enema shows
lesion as large irregular filling defect (arrows) in malrotated
cecum.
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Results
On CT images, two of the patients' colonic villous tumors showed a
convoluted gyral IV contrast-enhancement pattern (Figs.
1A and
2A). Grossly, the lesion in
Figure
1A,1B
was a large 11.5 x 6.0 cm cecal villous adenoma. Histologically, the
lesion showed carcinoma arising in a villous adenoma with focal invasion of
the submucosa, abutting the muscularis propria. The cecum was in the left
upper quadrant because of malrotation. The lesion in Figure
2A,2B,2C
was a 6.0 x 4.5 cm rectal villous adenoma with multifocal intramucosal
carcinoma but no invasion of the submucosa.
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Fig. 2C. —6.0 x 4.5 cm villous adenoma of rectum in 76-year-old
man. Photomicrograph of histologic specimen obtained from patient shows
villous architecture with increased surface area and vascularity
(arrows). (H and E, x100)
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On CT images, villous tumors of the other two patients appeared to have
irregular surface patterns coated by oral contrast medium, which produced a
corrugated appearance. The lesion in Figure
3A,3B,3C,
a sessile 4.0 x 4.0 cm polypoid villous adenoma in the descending colon,
also showed an unusual cluster of vessels adjacent to the tumor
(Fig. 3A). Microscopically, the
lesion had focal moderate dysplasia. Finally, gross examination of a fourth
lesion revealed a 5.0 x 5.0 cm villous tumor with a velvety appearance.
It was further described as a well-differentiated adenocarcinoma arising in a
villous adenoma with infiltration into the muscularis propria.
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Fig. 3A. —4.0 x 4.0 cm villous adenoma in 83-year-old woman.
Polypoid lesion (large arrow) visible on CT scan with lumen collapsed
around it. Mass has oral contrast in its interstices producing corrugated
pattern. Unusual cluster of mesenteric vessels (small arrows) is
adjacent to lesion.
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Fig. 3B. —4.0 x 4.0 cm villous adenoma in 83-year-old woman. CT
scan reveals contiguous section 7 mm superior to A. Lesion is filling
defect (black arrows) within opacified lumen. Prominent vessel
(white arrows) is in continuity with cluster of mesenteric vessels in
A.
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Discussion
Villous adenomas are premalignant lesions that constitute approximately 10%
of colonic adenomas, occur equally in both sexes, and are most frequently
found in patients who are between the ages of 50 through 80. Histologically,
villous adenomas arise from surface epithelium and are composed of papillary
fronds lined by mucin-producing columnar epithelium with slender fibrovascular
cores
[3,4,5,6].
In comparison with normal colonic mucosa, the villous configuration of the
epithelium in these lesions produces an increased surface area (Figs.
2B and
2C). The markedly increased
proportion of epithelium to connective tissue is also thought to produce a
soft, velvety, and compressible quality to these lesions
[4]. They are distinguished
from tubular and tubulovillous adenomas by the presence of 10 or more lobules
and by their increased propensity for malignant transformation
[5]. However, villous adenomas
may grow as large as 10-15 cm while remaining benign. They most commonly occur
in the rectum and rectosigmoid, but they may occur anywhere in the colon as
well as the rest of the gastrointestinal tract.
Villous adenomas are usually sessile lesions, but they may be polypoid or
broad, flat, and carpetlike. Although villous adenomas tend to bleed less than
other adenomas and are often asymptomatic, larger lesions may obstruct the
bowel or bleed, particularly in the context of malignant transformation.
Clinically, excessive mucus secretion may lead to diarrhea and electrolyte
losses, especially loss of potassium
[1,2,3,4,5,6,7].
Radiographically, on barium enema, villous adenomas are often soft, thereby
permitting moderate changes in size and shape on compression films. Typically,
villous adenomas produce a sessile filling defect with an irregular mucosal
pattern that has been referred to as reticular, granular, lacy, or feathery.
This appearance is due to the collection of barium in the interstices of the
adenomas' frondlike excrescences
[4,5,6,7].
In two of our patients' CT studies, a similar phenomenon was observed as the
oral contrast medium became trapped in the villous interstices, producing an
analogous corrugated appearance (Fig.
3A,3B,3C)
in the surface pattern.
In the other two patients' CT studies, large villous tumors had a gyral
pattern, likely produced by the IV contrast enhancement (Figs.
1A and
2A) superimposed on a
low-attenuation background within the adenomas. The low-attenuation areas in
the rectal villous adenoma in Figure
2A,2B,2C
ranged from 15 to 17 H, likely because of high mucus content. Also, in the
patient represented in Figure
2A,2B,2C,
the villous architecture and its increased surface area contributed to
increased vascularity (Fig.
2C). Superficial ulceration was also noted in this lesion and
likely increased the vascular component even further.
The phenomenon of increased vascularity in villous adenomas has been
described only once previously with non-CT imaging techniques. In an
angiographic analysis of villous tumors of the colon, Riba and Lunderquist
[8] described villous adenomas
as "richly vascularized tumors with distinct intense contrast stain in
the capillary phase and early mesenteric filling." This description may
well relate to the findings in our two CT patients whose tumors had a
convoluted, gyral pattern. Furthermore, a "brain-like" pattern of
a villous adenoma has recently been noted in a case report in which MR imaging
was used [3]. It is thought
that this surface gyral pattern could also be accentuated on CT images by
intense contrast enhancement in the capillary phase, superimposed on
mucus-related low-attenuation background, as noted in the two patients
discussed previously.
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Abstract
Introduction
