Abstract A case of a fibrovascular polyp of the sigmoid colon is reported. The patient tested positively for fecal occult blood on a mass survey for colorectal cancer, and underwent colonoscopic examination which revealed a pedunculated submucosal tumor in the sigmoid colon. The tumor, about 10mm in diameter, had a short thin stalk and was removed endoscopically; the histological diagnosis was fibrovascular polyp. This extremely rare polyp is discussed, and particular attention is focused on the unusual endoscopic features and on the appropriate management.

Key words: submucosal tumor, nonepithelial tumor, pedunculated tumor, colonoscopic polypectomy

^a Higashi Kanamachi Naika Clinic, 7-5-8-1 Higashi Kanamachi, Katsushika, Tokyo 125-0041, Japan.
^b Second Department of Pathology, Hirosaki University School of Medicine, 5 Zaifucho, Hirosaki, Aomori 036-8562, Japan.

Introduction

We recently encountered a case of colonic fibrovascular polyp that showed characteristic endoscopic features. Fibrovascular polyps, which are pedunculated submucosal tumors, are occasionally found in the esophagus,[1-8] but are extremely rare in the colon. The present report focuses on the diagnostic problems and on appropriate management.

Case report

A 72-year-old Japanese woman was referred to Mutsu General Hospital in Aomori Prefecture in August 1991 for follow up of positive fecal occult blood test (determined by reverse passive hemagglutination) conducted in a mass survey for colorectal cancer. She had no complaints and had had no changes in bowel habits. She was given a barium enema, which showed a polyp, about 1cm in diameter, in the sigmoid colon(Figs. 1,2). Subsequent colonoscopy revealed that the polyp was pedunculated and not ulcerated, and had a smooth surface, with the same color as the surrounding mucosa; the mucosa around the tumor appeared normal(Figs. 3,4). The polyp was elastic and easily indented by biopsy forceps(Fig. 5), but it did not spring back to its previous shape immediately after the biopsy forceps was opened. The biopsy specimens taken from its distal end showed normal colonic mucosa. The patient did not have an elevated sedimentation rate or eosinophilia. Upper gastrointestinal endoscopy revealed that the patient also had a duodenal ulcer. A tentative diagnosis of submucosal tumor was made and the tumor was endoscopically polypectomized, using a diathermy snare, with no complications such as perforation or hemorrhage occurring. It took time to excise the polyp. The excised polyp was 9x4x11mm in size. Histologically, the tumor consisted of fibrous tissue containing blood vessels and lymphatics; it was completely covered by normal colonic mucosa and by the muscularis mucosae(Fig. 6), but it contained a little blood. The mucosa covering the tumor was 0.6mm in thickness and had no vascular proliferation. The microscopic appearance was similar to that of a fibrovascular polyp of the esophagus. The fibrous core was stained blue with Azan stain, and blue violet with Weigert's fibrin stain, but did not stain blue with phosphotungstic acid hematoxylin(PTAH)stain. The patient had a favorable course and a barium enema 5 months later showed no recurrence.

Fig. 1. Barium enema demonstrates a small polyp of the sigmoid colon, about 1cm in diameter(arrow)

Fig. 2. High power view of Fig. 1. Barium enema demonstrates a small polyp with a smooth surface and slight depression(arrowheads)

Fig. 3. The polyp as seen during colonoscopy. Note the normal-appearing mucosa over the polyp

Fig. 4. The polyp as seen during colonoscopy. The polyp is attached to the colonic wall by a short thin stalk

Fig. 5. The polyp is easily depressed by biopsy forceps. It does not immediately return to its previous shape

Fig. 6. Microscopic appearance of the tumor. Normal adenic mucosa and lamina muscularis mucosae cover the tumor. The stroma consists of fibrovascular connective tissue. Note the blood vessels, lymphatics, and collagen interspersed within the stroma. HE, x8

Discussion

In one study,[9] a total of 376 cases of submucosal tumors of the large bowel were reported; 127 cases(34%)were benign tumors, including 47 leiomyomas, 42 lipomas, 11 lymphangiomas, and 10 hemangiomas. The other 249 cases were malignant submucosal tumors, and these constituted 1.3% of all cancers of the colon and the rectum.[9] Up to 80 cases of fibrovascular polyps of the esophagus have been reported; [1-8,17] however, we found no reports of a colonic fibrovascular polyp.

The gross endoscopic impression is heavily relied on in making a diagnosis. Because nonepithelial tumors are usually covered by normal mucosa, most of them are easily distinguishable from epithelial tumors. Some submucosal tumors, such as lipomas, lymphangiomas, and hemangiomas, have endoscopically characteristic findings.[10-15] Lipomas and lymphangiomas are smooth and softer than other tumors. Lipomas can usually be indented with closed biopsy forceps and tend to spring back rapidly to their previous shape upon withdrawal of the forceps, this being known as the "pillow," "cushion," or "tenting sign".[10,11] After the mucosa covering a lipoma is removed by the taking of multiple biopsies, fat can be seen protruding from the biopsy site; this is called the "naked fat sign."[12] Lymphangioma occurs as a fluctuant and cystic mass;[13] peristalsis, compression, and the patient's position changes its shape.[14] After the surface mucosa is removed, serous and clear liquid usually flow out from the biopsy site and its size is then reduced.[14] Most hemangiomas show endoscopically characteristic findings of small bluish discolorations or bright cherry-red spots.[15] The fibrovascular polyp seen in our patient did not have the above characteristic findings. It is thought to be characteristic that this tumor was easily depressed when grasped with biopsy forceps, and it did not spring back rapidly to its previous shape. The authors believed that the biopsy forceps had extruded the blood and lymph fluid from the fibrovascular polyp, causing the polyp not to spring back to its original shape. Usually it takes time to excise a submucosal tumor, because it is necessary to cut its muscularis mucosae.

Fibrovascular polyps are benign submucosal tumors, and are covered by normal mucosa that may be focally ulcerated. Histologically, these tumors consist of spindle cells, occasionally arranged in whorls, and loose vascular connective tissue. In such tumors of the esophagus, mononuclear cell infiltration varies from minimal to severe, and tends to be prominent distally; however, the present tumor showed only minimal chronic inflammation. Histological differential diagnosis is with other mesenchymal tumors, including fibromas, leiomyomas, and inflammatory fibroid polyps; the present tumor was not reminiscent of these tumors because of the lack of common histological features. The fibrous core was stained blue with Azan stain, indicating collagen fibers; the findings of PTAH staining indicated that this core did not consist of fibrin or fibrinoid as the result of congestion.

Rigorous histopathological examination is necessary to differentiate a fibrovascular polyp from the congestion and chronic inflammation resulting from idiopathic intussusception in the ileocecal area;[16] the polyp found in the present patient showed submucosal fibrovascular proliferation rather than simple congestion, and was accompanied by few inflammatory cells, without a whorl arrangement of stromal cells around vessels.

Lodmell[17] reported a patient with fibrovascular polyp of the esophagus whose presurgical laboratory findings showed eosinophilia and an elevated sedimentation rate; these findings were not shown in our patient.

The propulsive forces created by peristalsis, combined with the traction of the passing stool must lead, in the sigmoid colon, to the development of a pedunculated structure. Although it is possible that the fibrovascular polyp reported here was a secondary change of the submucosal fibrovascular tissue, its histogenesis is unclear.

The clinical manifestations of submucosal tumors of the colon are related to their size, and large submucosal tumors may cause intussusception. Like fibrovascular polyps of the esophagus, those of the colon may become large. This suggests that a fibrovascular polyp of the colon has the potential to cause intussusception. Most fibrovascular polyps of the esophagus are large and vascular; the routine removal of fibrovascular polyps of the esophagus is controversial. Patel et al.[2] reported one in which the length was 17cm and which had large vessels running throughout its core; they elected surgical excision. Siddins and Cade,[8] however, reported a case of a smaller fibrovascular polyp of the esophagus, 10cm in length, which was safely removed endoscopically. Diathermy polypectomy is not always dangerous in resecting smaller fibrovascular polyps of the esophagus. In the present patient, because of the polyp's small size and thin stalk, colonoscopic polypectomy was undertaken with adequate hemostasis, and the polyp was found to contain relatively few blood vessels histologically. If small fibrovascular polyps of the colon grow slowly, similar to those of the esophagus, it is necessary to remove them safely endoscopically before they grow, increase in vascularity and cause intussusception.

Since, to our knowledge, this is the first lesion of this kind ever encountered, it is obvious that there is no way to make an accurate diagnosis for polypectomy. Although the surgical resection of a submucosal tumor is usually undertaken due to its submucosal location,[18,19] polypectomy for a pedunculated submucosal tumor is a reasonable method when the tumor does not have features of hemangioma, because one can expect both exact histopathological diagnosis and complete resection, and the procedure is less harmful for the colonic wall. Accurate endoscopic diagnosis of submucosal tumors is difficult. In the series cited above, 249 of 376 submucosal tumors, 66% were shown to be malignant.[9]

References

[1]

Cochet B, Hohl P, Sans M, et al. Asphyxia caused by laryngeal impaction of an esophageal polyp. Arch Otolaryngol 1980; 106: 176-178.

[2]

Patel J, Kieffer RW, Martin M, et al. Giant fibrovascular polyp of the esophagus. Gastroenterology 1984; 87: 953-956.

[3]

Walters NA, Coral A. Case reports. Fibrovascular polyp of the esophagus: The appearances on computed tomography. Br J Radiol 1988; 61: 641-643.

[4]

Penagini R, Ranzi T, Velio P, et al. Giant fibrovascular polyp of the oesophagus: Report of a case and effects on oesophageal function. Gut 1989; 30: 1624-1629.

[5]

Whitman GJ, Borkowski GP. Giant fibrovascular polyp of the esophagus: CT and MR findings. AJR 1989; 152: 518-520.

[6]

Avezzano EA, Fleischer DE, Merida MA, et al. Giant fibrovascular polyps of the esophagus. Am J Gastroenterol 1990; 85: 299-302.

[7]

Timmons B, Sedwitz JL, Oller DW. Benign fibrovascular polyp of the esophagus. South Med J 1991; 84: 1370-1372.

[8]

Siddins M, Cade R. Fibrovascular polyp of the oesophagus. Aust NZ J Surg 1991; 61: 237-240.

[9]

Watanuki K(ed). Proceedings of the 11th Congress of the Japanese Society for Cancer of Colon and Rectum: Survey of non-epithelial tumors of the large intestine by questionnaire(revised edition)(in Japanese).Tokyo: First Dept of Surgery, The Jikei Univ School of Med, 1980; 1-95.

[10]

De Beer RA, Shinya H. Colonic lipomas: An endoscopic analysis. Gastrointest Endosc 1975; 22: 90-91.

[11]

Rand AR. Colonic lipoma(a selection of photographs from the 1980 ASGE "learning corner"). Gastrointest Endosc 1981; 27: 40-41.

[12]

Messer J, Waye JD. The diagnosis of colonic lipomas. The naked fat sign. Gastrointest Endosc 1982; 28: 186-188.

[13]

Kuroda Y, Katoh H, Ohsato K. Cystic lymphangioma of the colon. Dis Colon Rectum 1984; 27: 679-682.

[14]

Kuramoto S, Sakai S, Tsuda K, et al. Lymphangioma of the large intestine. Report of a case. Dis Colon Rectum 1988; 31: 900-905.

[15]

Allred HW Jr, Spencer RJ. Hemangiomas of the colon, rectum, and anus. Mayo Clin Proc 1974; 49: 739-741.

[16]

Kitazumi K, Kogawa T, Ichikawa H, et al. Idiopathic intussusception at the ileocecal region in adults. Report of a case. J Kyoto Prefect Univ Med 1988; 97: 315-319.

[17]

Lodmell LA. Giant benign esophageal polyp. Gastroenterology 1955; 29: 1077-1082.

[18]

Khawaja FI. Pedunculated lipoma of the colon: Risks of endoscopic removal. South Med J 1987; 80: 1176-1179.

[19]

Kadakia SC, Kadakia AS, Seargent K. Endoscopic removal of colonic leiomyoma. J Clin Gastroenterol 1992; 15: 59-62.

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The original report was published in J Gastroenterol 1994;29:763-766.