Pseudotumor of the Sigmoid Mimicking Carcinoma

• Introduction
• Case Report
• Discussion
• References

On colonoscopy, the macroscopic aspect of a lesion is an important criterion for the differential diagnosis. We present a case of an apparently malignant tumor in the sigmoid. Histological investigation failed to support the diagnosis made from the gross appearance seen on colonoscopy. After surgical resection, the lesion turned out to be a reactive pseudotumor caused by fibroepithelial hyperplasia related to a severe diverticulitis with perforation of the intestinal wall.

Introduction

The macroscopic aspect of a lesion detected using colonoscopy plays an important role with respect to diagnostic and therapeutic consequences, especially when a malignoma is suspected. A diagnosis derived from this aspect usually has to be confirmed and clarified by biopsy with histological examination and by different imaging techniques. We describe a case of a pseudotumor of the sigmoid which presented as malignoma on colonoscopy. Histological examination did not prove the diagnosis but supported it by describing an adenoma. Only after surgical resection did it become clear that the tumor was not malignant but a benign pseudotumor caused by fibroepithelial hyperplasia on the base of a severe diverticulitis. Data in the literature relating to this complication of diverticulitis are very limited and with this case we present an impressive example of a rare pitfall that can occur with colonoscopy.

Case Report

A 73-year-old, white man presented to our clinic complaining of diarrhea with fresh blood and mucus, which had lasted for several days. Some years previously, an appendectomy and a herniotomy of a right inguinal hernia had been carried out. During the last few years, several basal cell carcinomas and squamous cell carcinomas in situ had been removed from the skin of the patient's head. His past medical history was otherwise unremarkable. The family history was negative with regard to colonic adenomas or colorectal carcinoma. Digital rectal examination revealed blood and mucus, but no palpable mass. There were no other abnormal physical findings. Routine laboratory examinations showed elevated fibrinogen (531 mg/dl), C-reactive protein (5.6 mg/dl), and alkaline phosphatase (225 U/l), as well as significant leukocytosis (16.3/nl). All other laboratory parameters including carcinoembryonic antigen were within normal limits.

Abdominal ultrasonography revealed a thickened section of intestinal wall (17 mm) in the left lower abdominal quadrant, which extended into the small pelvis. No metastases in the liver or enlarged lymph nodes were seen. Total ileocolonoscopy showed some diverticula in the sigmoid colon. Approximately 25 cm ab ano, a lesion with a macroscopic aspect highly suspicious of malignoma was detectable (Figure [1]). Several exophytic parts of the tumor protruded into the lumen (Figure [2]), but there was no significant stenosis in the region of the tumor. Snare polypectomy of one of the protruding parts was performed. Histological examination of this piece, of approximately 1 cm in diameter, showed mucosa of the sigmoid with parts of a tubular adenoma with epithelial dysplasia grade 2.

Because of the macroscopic aspect which was highly suspicious of a malignant tumor, we suggested a surgical resection of the mass, although histological investigation had only revealed an adenoma. Excision was then performed by resection of the rectosigmoid and descendorectostomy. The resected material was examined histologically and showed a severe diverticulosis with diverticulitis. In contrast to the initial examination of material retrieved endoscopically, no adenomatous tissue could be detected in multiple sections of the resection specimen. Partial perforation of a diverticulum had occurred and was accompanied by an extensive inflammatory reaction of all layers of the wall and perisigmoiditis and periproctitis (Figures [3] [4] ). The macroscopically suspected tumor measured 2.5 × 3.5 cm and was found to be a pseudotumor caused by fibroepithelial hyperplasia related to a perforated diverticulitis with extensive transmural inflammation. The postoperative course of the patient was uneventful and after 2 weeks he was discharged from hospital.

Discussion

The macroscopic aspect on colonoscopy is one of the main criteria in the diagnostic algorithm of suspected colorectal malignoma, along with history and clinical findings. The diagnosis is usually confirmed by biopsy. Staging is then carried out using different imaging techniques. In this case of a patient with an exophytic lesion in the sigmoid, histological examination of the specimen from initial snare polypectomy revealed normal mucosa with parts of a tubular adenoma with epithelial dysplasia grade 2. It was suspected that the endoscopic excision had not captured the invasive portion of the malignoma, and therefore surgical resection was performed. However, histological examination of the resected material showed a completely different setting. The exophytic tumor turned out to be a protruding fibroepithelial hyperplasia on the base of a severe perforated diverticulitis. The initially described parts of tubular adenoma could not be seen on multiple sections of the resected tissue. We found a small lesion of the mucosa suggesting that the adenomatous tissue had been removed completely by snare polypectomy. It can be concluded that in this particular case the inflammatory tumor also bore adenomatous tissue, which had led to the preliminary diagnosis of possible malignoma.

Diverticulosis is a widespread condition in the elderly with a rate of 30 - 50 % in those over 70 years. It is estimated that this usually asympatomatic condition leads to complications (diverticulitis) in about 20 % of cases. The etiology is multifactorial, with disturbance of bowel motility, chronic constipation, obesity, low fiber diet and lack of exercise being some of the most important risk factors [1]. Acute diverticulitis may present dramatically with severe pain and life-threatening complications. On the other hand, recurrent acute inflammation often shows only minor symptoms and may resolve either untreated or with conservative treatment. However, frequent recurrence over months and years finally leads to a chronic state with complications such as fistula, free or covered perforation, and inflammatory or fibrous stricture. Cell proliferation at the site of inflammation as well as fibrosis and angiogenesis result from several cytokines (e. g. interleukin-1, tumor necrosis factor-alpha) released by activated leucocytes [2]. Shrinking of the wall may lead to subtotal or complete obstruction of the bowel lumen [3]. This situation may mimic colon carcinoma which coincides with diverticulosis/diverticulitis in 10 - 20 %. Therefore, it is very important to differentiate between benign inflammation and malignant tumor, by means of biopsy and histological examination, prior to making decisions concerning therapy. In our case, we were misled by the macroscopic aspect and an initial description of adenoma, and surgery was peformed although there was no significant stenosis of the lumen. Surgical resection is the treatment of choice in specific inflammatory pseudotumor [4], or when the urinary bladder is affected by the tumor [5], and in cases of perforation or fistula. Since covered perforation was the reason for the pseudotumor, surgery was considered to be the appropriate treatment in the case of our patient.

From this case, we conclude that inflammatory pseudotumor should be considered a possibility when the macroscopic aspect of a lesion on colonoscopy suggests malignancy but biopsies fail to prove the diagnosis.

References

• 1 Hotz J. Divertikelkrankheit. In: Hahn EG, Riemann JF (eds). Klinische Gastroenterologie.  Stuttgart; Thieme, 1996: 929-940
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• 2 Mitchell R N, Cotran R S. Chronic inflammation. In: Kumar VK, Cotran RS, Robbins SL (eds). Basic pathology. 6th ed.  Philadelphia; Saunders, 1997: 41-43
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• 3 Paul F, Altaras J. Divertikulose - Divertikulitis.  Z Gerontol. 1982;  15 70-78
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• 4 Aalbers A GJ, De Wilt J HW, Zondervan P E, Ijzermans J NM. A colon-derived inflammatory pseudotumor.  Dig Dis Sci. 1999;  44 578-581
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• 5 Kitamura M, Namiki M, Nonomura N, et al. A pseudotumor of the urinary bladder secondary to diverticulitis of the sigmoid colon with colo-vesical fistula: a case report.  Urol Int. 1987;  42 234-236
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A. Rosenbaum, M.D.

Medizinische Klinik C Klinikum der Stadt Ludwigshafen

Bremserstrasse 79 67093 Ludwigshafen Germany

Fax: Fax:+ 49-621-5034114

Email: E-mail:MedCLu@t-online.de

References

• 1 Hotz J. Divertikelkrankheit. In: Hahn EG, Riemann JF (eds). Klinische Gastroenterologie.  Stuttgart; Thieme, 1996: 929-940
  Search in Google Scholar
• 2 Mitchell R N, Cotran R S. Chronic inflammation. In: Kumar VK, Cotran RS, Robbins SL (eds). Basic pathology. 6th ed.  Philadelphia; Saunders, 1997: 41-43
  Search in Google Scholar
• 3 Paul F, Altaras J. Divertikulose - Divertikulitis.  Z Gerontol. 1982;  15 70-78
  PubMedSearch in Google Scholar
• 4 Aalbers A GJ, De Wilt J HW, Zondervan P E, Ijzermans J NM. A colon-derived inflammatory pseudotumor.  Dig Dis Sci. 1999;  44 578-581
  CrossrefPubMedSearch in Google Scholar
• 5 Kitamura M, Namiki M, Nonomura N, et al. A pseudotumor of the urinary bladder secondary to diverticulitis of the sigmoid colon with colo-vesical fistula: a case report.  Urol Int. 1987;  42 234-236
  PubMedSearch in Google Scholar

A. Rosenbaum, M.D.

Medizinische Klinik C Klinikum der Stadt Ludwigshafen

Bremserstrasse 79 67093 Ludwigshafen Germany

Fax: Fax:+ 49-621-5034114

Email: E-mail:MedCLu@t-online.de