Filiform polyposis with sigmoid colon adenocarcinoma: a case report
Filiform polyposis is a rare form of inflammatory polyposis, which is occasionally formed in the colon of patients with history of inflammatory bowel disease (IBD). It is characterized by presence of several to hundreds of slender, worm-like polyps in the colon lined by histologically normal colonic mucosa and often coalesce, resulting in a tumor-like mass. Filiform polyposis is most frequently associated with a post-inflammatory reparative process in patients with IBD history, and only cases of filiform polyposis occurring in patients without IBD history have been reported. Filiform polyposis has been considered as a benign inflammatory polyposis without any risk of dysplasia, while the possibility of carcinogenesis of inflammatory polyps is not fully excluded. To date, only three cases of filiform polyposis coexisting with dysplasia have been reported.
A 59-year-old male patient with no past medical history of IBD underwent laparoscopic sigmoidectomy for obstructive filiform polyposis, which was associated with sigmoid colon adenocarcinoma. Based on the histological findings of the resected specimen, invasive sigmoid colon adenocarcinoma was surrounded by filiform polyposis, and adenocarcinoma also scattered uniformly on the surface of filiform polyposis. In immunohistochemistry, abnormal p53 expression was observed in adenocarcinoma, while it was not shown in mucosa on filiform polyposis.
This is the fourth case of filiform polyposis that is closely associated with colon dysplasia or adenocarcinoma based on histological findings. However, immunohistochemical findings did not support the theory that inflammation initiates adenocarcinoma in filiform polyposis like IBD. Hence, further immunohistochemical and genetic analyses are needed to clarify the association between filiform polyposis and carcinogenesis.
KeywordsFiliform polyposis Colon Adenocarcinoma Dysplasia Inflammatory carcinogenesis
Inflammatory bowel disease
Filiform polyposis is a rare form of inflammatory polyposis that is occasionally formed in the colon of patients with history of inflammatory bowel disease (IBD). Filiform polyposis is characterized by presence of several to hundreds of slender, worm-like polyps in the colon lined by histologically normal colonic mucosa . Polyps often present as multiple mucosal projections that can reach up to 100 mm as in this case, and the term giant inflammatory polyposis has been used to describe these kinds of polyposis . Filiform polyposis is most frequently associated with a post-inflammatory reparative process in patients with IBD history  and rarely associated with colon diverticulitis and intestinal obstruction in patients without IBD history [4, 5]. Filiform polyposis has been considered as a benign inflammatory polyposis without any risk of dysplasia , while the possibility of carcinogenesis of inflammatory polyps is not fully excluded . To date, three cases with filiform polyposis coexisting with dysplasia have been reported [7, 8, 9]. Herein, we report a case of filiform polyposis that is closely associated with sigmoid colon adenocarcinoma in a 59-year-old patient without IBD history.
A 59-year-old male patient was referred to our institution because of diarrhea and lower abdominal pain. He lost 6 kg of weight in 6 months. He did not have any personal or family history of polyps, colon cancer, and IBD. Physical examination revealed lower abdominal pain without tenderness and mass in the lower abdominal area. Blood examination revealed anemia (hemoglobin level 9.3 g/dl), hypoproteinemia (protein level 4.0 g/dl), and hypoalbuminemia (albumin level 1.2 g/dl). The carcinoembryonic antigen level was slightly increased (6.4 ng/ml).
The term filiform polyposis was first coined by Appelman in 1984, who used it to describe a syndrome involving the radiographic appearance of numerous long slender worm-like defects in the colon with a normal haustral pattern . Filiform polyposis is known as a rare inflammatory polyposis that occurs more frequently in patients with IBD history. Histologically, a polyp is characterized by dilated blood vessels and fibrovascular cores in submucosal tissues and covered with normal mucosa. Polyps vary greatly in number, from several to hundreds, and often coalesce, resulting in a tumor-like mass as in this case. Other terms, such as giant inflammatory polyposis and giant pseudopolyposis, have been used to describe these kinds of polyposis [2, 12]. The most common sites affected are the sigmoid colon and rectum , but polyposis can extend as far as the cecum and rarely occur in the stomach and small bowel .
In patients with IBD, long-term inflammation of the colonic mucosa with alternative periods of ulceration and healing is believed to be a prerequisite for the development of these worm-like polyps [3, 11]. Recently, rare cases of filiform polyposis in patients without history of IBD have been reported. In these cases, inflammatory cytokines  and the traction of redundant mucosa by intestinal peristalsis with hyperplasia and fibrosis of the intestinal wall, induced by colon diverticulitis, might relate to the development of filiform polyposis . Furthermore, filiform polyposis developed due to a circumferential tumor obstruction in the colon . In our case, hyperplasia of intestinal wall with sigmoid colon diverticulitis and tumor obstruction was observed in patients without IBD history. These findings are possibly associated with the development of filiform polyposis.
Filiform polyps are occasionally difficult to distinguish from “filiform serrated adenoma” based on their endoscopic appearance; hence, a biopsy or polypectomy is necessary to confirm the exact diagnosis . Biopsy is also important for numerous conglomerated polyps as in this case. When biopsy proved adenoma or adenocarcinoma, polyps should be removed through a colonoscope or surgical colectomy . When patients with filiform polyposis experiences symptoms such as bleeding and obstruction, the polyps should be removed . Furthermore, the presence of occult dysplasia is suspected [7, 8]. In our case, biopsy for obstructive filiform polyposis showed adenocarcinoma; hence, laparoscopic sigmoidectomy with level D3 lymph node dissection was performed. The resected specimen showed invasive sigmoid colon adenocarcinoma surrounded by filiform polyposis.
Filiform polyposis has been considered as a benign inflammatory polyposis without any risk of dysplasia , while the possibility of carcinogenesis of inflammatory polyps is not fully excluded . In our patient, invasive sigmoid colon adenocarcinoma coexisted with filiform polyposis, and adenocarcinoma also developed on the surface of filiform polyposis: histological findings showed the association between filiform polyposis and adenocarcinoma. To date, only three cases of tumor coexisting with filiform polyposis and dysplasia have been reported, which were similar to our case [7, 8, 9]. Boulagnon reported the case of filiform polyposis coexisting with mucinous ascending colon adenocarcinoma. Tubular adenoma and high-grade dysplasia also developed on filiform polyps. Molecular analysis of adenoma and adenocarcinoma revealed microsatellite stable status and absence of BRAF mutation; meanwhile, immunochemistry showed abnormal p53 expression in the adenoma and adenocarcinoma, but this was not observed in the mucosa of the polyps . In our case, immunohistochemistry using anti-p53 and anti-Ki67 revealed that the erosive mucosa on filiform polyps showed neither proliferation abnormality nor p53 abnormal expression, while the adenocarcinoma showed an abnormal p53 nuclear expression. Since p53 mutations were observed in the inflamed mucosa in the early stage of inflammatory carcinogenesis , these findings do not suggest inflammatory carcinogenesis of filiform polyposis. Furthermore, the tumor found in our patient exhibited the same type of dysplasia: this finding was more suggestive of an incidental combination of two distinct pathological entities than carcinogenesis from inflammatory polyps.
Hence, we suggested the following model of tumor development in our case. First, sigmoid colon adenocarcinoma subcircumferentially existed; then filiform polyposis was formed by an inflammation of colon diverticulitis and the obstruction. Second, filiform polyposis was formed by an inflammation of colon diverticulitis; then the obstruction caused an implantation of sigmoid colon adenocarcinoma to erosive mucosa of filiform polyposis. Colon adenocarcinoma rarely develops in the defective part of mucosa . Third, collision between sigmoid colon adenocarcinoma and the malignant transformation of filiform polyposis possibly occurred. Either way, the coexistence of advanced cancer and widely spreading mucosal cancer could not be fully explained.
This is the fourth case of filiform polyposis that is closely associated with colon dysplasia or adenocarcinoma. However, immunohistochemical analysis of p53 mutation did not support the theory that inflammation triggered the occurrence of adenocarcinoma in filiform polyposis. Hence, immunohistochemical and genetic analyses are needed to clarify the relationship between filiform polyposis and carcinogenesis.
TO contributed to the design of the work, acquisition and analysis of data, drafting of the work and surgery. TK contributed to the drafting of the work and surgery. HK contributed to the acquisition and analysis of data. HA and KY contributed to the acquisition of data and surgery. SI revised the work. All authors read and approved the final manuscript.
No funding was received for this study and/or publication.
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Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the editor-in-chief of this journal.
The authors declare that they have no competing interests.
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