INTRODUCTION

Polypoid lesions of the gastrointestinal (GI) tractare common and divergent. Most of the polyps areepithelial in origin but polypoid mesenchymal pro-liferations and inflammatory lesions are also enco-untered. Although most of the polyps, especiallythose with epithelial features, can be diagnosedaccurately, there are some polyps that cannot beclassified easily under a certain category. Thisparticularly applies to mesenchymal cell prolifera-tions in most of the cases. Benign fibroblasticpolyp of the colon (BFPC) is a distinctive type ofmucosal polyp of the colorectum described by Es-lami-Varzaneh et al. in 2004 (1). It is composed ofbenign-appearing spindle cells in the lamina prop-ria leading to a wide separation and disorganizati-on of the colonic crypts. We are aware of 32 casesreported to date under the proposed terminology(2-4). Most of the cases were located in the sigmo-id colon (1, 3). Patients are generally asymptoma-tic or have a history of mild rectal bleeding (2). Al-most all lesions were detected on routine scree-

ning colonoscopy but were identified as nonspeci-fic “polyps” (1). They are small lesions measuring0.2 cm to 1.5 cm (1, 3). They are solitary polyps butaccompanied by various lesions, mainly tubularadenoma, hyperplastic polyps or diverticulosis (1-4). BFPC is morphologically and immunohistoche-mically distinct from other mesenchymal polypsand appears to be relatively rare, constituting abo-ut 0.2-1.5% of all colonic polyps according to theprevious reports (1, 4). BFPC follows an indolentcourse. None of the reported cases recurred duringa maximum follow-up period of 36 months (mean:18 months) (2). We present a case interpreted asBFPC and discuss it together with the differentialdiagnostic considerations.

CASE REPORT

A 50-year-old man, who had been operated two ye-ars before for rectal carcinoma and had remainedasymptomatic since then, underwent a routine fol-

Turk J Gastroenterol 2009; 20 (4): 287-290

Manuscript received: 08.01.2008 Accepted: 25.09.2008

doi: 10.4318/tjg.2009.0029

Address for correspondence: Baflak DO⁄ANAVfiARG‹LEge University, Faculty of Medicine Department of Pathology35100 Bornova, Izmir -TurkeyPhone: + 90 232 388 10 25 • Fax: + 90 232 373 61 43E-mail: bdoganavsargil@yahoo.com

Benign fibroblastic polyp of the colon: A case reportKolonun benign fibroblastik polibi: Olgu sunumu

Baflak DO⁄ANAVfiARG‹L1, Gürdeniz SER‹N1, Murat AKYILDIZ2, Yeflim ERTAN1, Müge TUNÇYÜREK1

Departments of 1Pathology, 2Gastroenterology, Ege University, School of Medicine, ‹zmir

Gastrointestinal kanalda, belirli bir kategori alt›nda s›n›flana-mayan çok say›da polip vard›r. Daha önce rektum karsinomunedeniyle opere edilmifl 50 yafl›ndaki bir erkek hastada izlenen,ve bilinen bir polip kategorisine yerlefltirilemeyen 6 mm çapl›sigmoidal bir polip sunulmaktad›r. Fokal bir erozyonun eflliketti¤i, baz› alanlarda inflamatuvar fibroid polip kuflkusu uyan-d›ran ve histolojik olarak kriptleri birbirinden ay›rarak dizilimbozuklu¤una yol açm›fl, benign görünüfllü bir i¤si hücre prolife-rasyonu ile karakterli olan lezyon, yak›n zamanda, Eslami-Varzaneh ve ark. taraf›ndan tan›mlanan, “Kolonun benign fib-roblastik polibi” hastal›k spektrumu içerisinde de¤erlendiril-mifltir. Olgu, ay›r›c› tan› kriterleri ve literatür bilgileri eflli¤in-de tart›fl›lm›flt›r.

Anahtar kelimeler: Stroma, fibroblastik, kolonik polip

There are a fair number of polyps in the gastrointestinal tract,which cannot be classified under a certain category. We reportherein a 50-year-old man with a 6-mm sigmoidal polyp; he hadbeen operated previously for rectal carcinoma. The polyp wascharacterized by benign-appearing spindle cells in the laminapropria leading to a wide separation and disorganization of thecolonic crypts, accompanied by focal erosion and restricted are-as suspicious for inflammatory fibroid polyp. The histologic fe-atures were found consistent with the disease spectrum of “be-nign fibroblastic polyp of the colon” defined by Eslami-Varza-neh et al. The case is presented with a review of the literatureand differential diagnostic considerations.

Key words: Stroma, fibroblastic, colonic polyps

DO⁄ANAVfiARG‹L et al.288

low-up colonoscopy, which revealed a 6-mm poly-poid lesion in the sigmoid colon. The polyp was farfrom the anastomosing line and nothing extraordi-nary was found in the rest of the colon. The pati-ent had neither a previous biopsy at the currentpolypectomy site, nor a history of infection or drugintake. The polyp was extirpated in a subsequentcolonoscopy session. On histologic examination, adisorganization was observed in the mucosal arc-hitecture at low power. The crypts were separatedfrom each other and a fibroblastic proliferation ac-companied by edema was observed in the interve-ning lamina propria (Figure 1A). A focal erosionwas noted in the surface epithelium but apartfrom those areas no apparent inflammatory cellswere present. A very few eosinophil leukocytes,mast cells and plasma cells were noted scattered

elsewhere between the crypts, mainly at the baseof this eroded area (Figure 1B). Between this mild-ly inflamed area and fibroblastic area there was avague zone where the bundles of spindle cells we-re more prominent (Figure 1C). The spindle cellsin the lamina propria were uniform and bland, thenuclei were oval to fusiform, and nucleoli and thecell borders were indistinct. In deeper parts of thepolyp, there were a few cystically dilated glands,the lining epithelium of which was attenuated. Fa-int concentric arrangements of spindle cells wereobserved around glands but not around the bloodvessels (Figure 1D). The vasculature was also notprominent. The cells showed no significant nucle-ar pleomorphism or hyperchromasia. No apparentnecrosis or mitosis was observed. Immunohistoc-hemical examination applied to rule out possible

FFiigguurree 11.. ((AA)) Low power view of the polyp. The crypts were separated from each other and a fibroblastic proliferation accompaniedby edema was observed in the intervening lamina propria. Cystically dilated deeper parts of the lesion were noted (hematoxylin andeosin [H&E], x4). ((BB)) Fibroblasts admixed with scattered eosinophils and plasma cells (H&E, x40). ((CC)) The zone observed betweenthe inflamed area and fibroblastic area (H&E, x10). ((DD)) Concentric arrangement of fibroblasts around glands (H&E, x20).

spindled cell proliferations as gastrointestinalstromal tumor (GIST), smooth muscle tumors,neural tumors, or inflammatory fibroid polyps re-vealed vimentin positivity, but CD117, CD34, S-100, desmin, smooth muscle actin and CD21 werenegative. We observed neither admixed hyperplas-tic changes nor adenomatous polyps in the vici-nity. No recurrence was seen in the follow-up in-terval of 18 months.

DISCUSSION

Benign fibroblastic polyp of the colon (BFPC) is adistinctive type of mucosal polyp of the colorec-tum. To our knowledge, 32 cases have been repor-ted as benign fibroblastic polyp in the literature.Nineteen of these cases were located in the sigmo-id colon, followed by five cases in the rectum, twocases in the rectosigmoid, and two cases in thedescending colon. One case was observed in the as-cending colon, splenic and hepatic flexures andright colon. Age of the patients ranged from 37 to84 years (1). There is a reported female predomi-nance (1-3).

In routine practice, GI pathologists have to copewith a considerable amount of “unnamed or not ot-herwise specified” polyps. Among these, mesench-ymal type polyp is rare and usually benign butmust be distinguished from GIST. Luckily, immu-nohistochemical examination is extremely usefulin differentiating these lesions. In the presentedcase, we ruled out a “GIST with very low malig-nant potential” (5) by absence of immuno-expres-sion for CD117 and CD34. The main differentialdiagnosis of mesenchymal polyps also includessmooth muscle or peripheral nerve sheath tumor,ganglioneuroma, smooth muscle hamartomas andprolapse-related changes (6). They could have be-en ruled out based on histology alone, but negati-vity of S-100, desmin, and smooth muscle actinwas also supportive. We suspected the lesion to bea nonspecific response to a nonspecific injury. The-re was focal erosion in the surface epithelium anda mild inflammation. The lesion itself was slightlyedematous, and there were cystically enlargedglands. Thus, regarding the fibroblastic prolifera-tion, the overall picture would have fit a nonspeci-fic tissue response. Reserving this possibility, wecan argue against the diagnosis of a simple tissueresponse. Surface erosion was focal and was notaccompanied by a prominent granulation tissue. Itwas not reported in the first colonoscopy and se-ems to be the result rather than the cause of the

tumefaction. Furthermore, surface erosion was re-ported in some of the BFPCs (2) as well as the pos-sibility of being the end result of local inflammati-on that leads to exuberant scar tissue. In our case,the patient history did not reveal overt GI systeminflammation, drug usage or biopsy trauma at thecurrent polyp site. Mucosal prolapse syndromesare also considered in the differential diagnosisalthough not suspected clinically, but we did notobserve longitudinal extensions of smooth muscleemanating from the muscularis mucosae as in pro-lapse syndromes; however, this feature was alsoreported in some cases of BFPC (1).

We observed scattered eosinophils and an “onion-skin-like” spindle cell arrangement aroundglands. Although this pattern was restricted to afew glands, it raised the possibility of an inflam-matory fibroid polyp (IFP) (Vanek’s tumor) (7).However, perivascular spindle cell arrangement ismore common in IFP and eosinophil infiltration ismore prominent (8). Furthermore, it is more com-mon in the stomach and very rare in the colon (9).However, the reporters of the case series, inclu-ding Eslami-Varzaneh, point to some similaritiesbetween IFP and BFPC and admit that the lesionmay represent an early stage of the disease (1-4).Zamecnik et al. (4) evaluated markers of dendriticcells in four of their cases and found occasionalCD34 and consistent fascin reactivity. They sug-gested that BFPC might be related to an inflam-matory fibroid polyp, which is proposed as origina-ting from dendritic cells. The main objection tothis hypothesis is the electron microscopic featu-res, which are supportive of fibroblastic differenti-ation, in lesions so-called BFPC (1). In our case,we interpreted the spindle cells as fibroblasts sin-ce they expressed vimentin only and lacked reacti-vity for markers of specific differentiation inclu-ding CD21, a marker for dendritic cell differenti-ation. However, we were unable to perform elec-tron microscopic evaluation. We are aware of thelimitations in our case but given the histologic fe-atures presented above, we believe that our case issomehow different from the classified “polyps” or“inflammatory conditions”, and it may represent astep in the spectrum of BFPC. Although the lesionis reported to be rare, we suspect that it can bemore frequent than presumed. These are smalland benign-looking polyps in which surveillancecan be preferred rather than extirpation. Moreo-ver, there is a possibility for the pathologists to tryand fit them under a “known” category or to avoid

Fibroblastic polyp 289

naming them and just interpret on histologic ap-pearance.

In conclusion, BFPC is likely to represent a dis-tinct site-specific mesenchymal lesion of the colon.

Further studies and case presentations are neededto reveal its characteristics as well as the actuallink between the proposed entity and inflammati-on and IFP.

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