CT and MR imaging findings of sinonasal angiomatous polyps

European Journal of Radiology 83 (2014) 545–551Contents lists available at ScienceDirectEuropean Journal ofRadiologyj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e j r adCT and MR imaging findings of sinonasal angiomatous polypsJing Zou a ,1,Fengyuan Man b ,1,Kai Deng c ,Yuanyuan Zheng a ,Dapeng Hao a ,∗,Wenjian Xu a ,∗∗aDepartment of Radiology,The Affiliated Hospital of Qingdao University,Qingdao,Shandong,China bDepartment of Radiology,Beijing Tongren Hospital,Capital Medical University,Beijing,China cDepartment of Radiology,Qingdao No.4People’s Hospital,Qingdao,Shandong,Chinaa r t i c l ei n f oArticle history:Received 17June 2013Received in revised form 28November 2013Accepted 5December 2013Keywords:Tomography,X-ray computed Magnetic resonance imaging Paranasal sinus diseases Hemangioma Nasal polypsa b s t r a c tObjective:To characterize the CT and MR imaging findings of patients with sinonasal angiomatous polyps (SAPs)and evaluate their respective clinical value in the diagnosis of SAP.Methods:CT and MR imaging findings of 15patients with pathologically proven SAP were examined.Assessed image features included location,size,margin,attenuation,and change of the bony walls of the sinonasal cavity on CT,and signal intensity and enhancement pattern on MR.Results:On CT,the SAP was mostly isoattenuated with patches of slight hyperattenuation.Most lesions caused changes in the adjacent bone,including expansile remodeling (n =8),defect or destruction (n =7),and hyperostosis (n =6).All lesions examined by MR showed heterogeneous isointense signal inten-sity on T1-weighted images and mixed obvious hyperintense and hypointense signal intensity with linear hypointense septum internally (n =10),and hypointense peripheral rim on T2-weighted images (n =10).Postcontrast MR images demonstrated areas of heterogeneous and marked enhancement with an unenhanced hypointense rim and septa (n =7).Conclusions:CT and MR imaging have respective advantages in the diagnosis of bined application of CT and MR examinations is necessary for patients with suspected SAP.© 2013 Elsevier Ireland Ltd. All rights reserved.1.IntroductionSinonasal angiomatous polyp (SAP)is a rare benign and non-neoplastic lesion.It is primarily composed of extensively hyperplastic and dilated vessels with scanty inflammatory infiltra-tion and abundant extracellular fibrin [1,2].Although inflammatory sinonasal polyp (SNP)is the most common non-neoplastic sinonasal mass examined pathologically,as a special subtype SAP only accounts for 4–5%of all SNPs [1].Simple conservative surgical excision of SAP is curative,and postoperative recurrence is rare.Therefore,correct preoperative diagnosis of SAP is important lest patients undergo unnecessary extensive surgery [3].SAP may show similar imaging features with sinonasal masses,such as other SNP,inverted papilloma,fungus ball,capillary hemangioma,juvenile angiofibroma and some pos-sibly malignant tumors [2,4,5].To the best of our knowledge,there have been only a few studies describing the imaging features of SAP∗Corresponding author at:Department of Radiology,The Affiliated Hospital of Qingdao University,16Jiangsu Road,Qingdao,Shandong,China.Tel.:+8653282911500.∗∗Corresponding author.Tel.:+8653282911585.E-mail addresses:haodp 2009@ (D.Hao),cjr.xuwenjian@ (W.Xu).1Both of them contributed equally and both of them are first author.[1–8].The purpose of this study was to report the characteristic CT and MR imaging findings of SAP in the sinonasal cavity.2.Materials and methods2.1.PatientsThe present study was approved by the institutional review board.Between July 2008and February 2013,a total of 15patients with pathologically proven SAP were retrospectively reviewed.The patients included five men and 10women,age range from 12to 81years,with a mean age of 42.7years.CT (n =13)and MR (n =10)images of these 15patients were retrospectively reviewed.Among these 15cases,two patients had a history of craniofacial trauma 2days and 2years previously,respectively.Furthermore,one patient underwent endoscopic sinus surgery to excise a nasal polyp 20years previously,and there had been massive bleeding from the ipsilateral nasal cavity 5years previously without appar-ent cause.The duration of symptoms before diagnosis ranged from 20days to 20years (median,12months).All 15patients underwent surgical excision of SAP by endoscopic sinus surgery.2.2.Imaging techniquesAmong the 15patients,CT scanning was performed in 13patients and MR imaging in 10patients.Eight patients underwent0720-048X/$–see front matter © 2013 Elsevier Ireland Ltd. All rights reserved./10.1016/j.ejrad.2013.12.002546J.Zou et al./European Journal of Radiology 83 (2014) 545–551Fig.1.Axial CT scan with a bone algorithm (a)shows an expansile mass (asterisk)centered in the right maxillary sinus.Expansile remodeling and thinning of the medial wall is observed (arrow).Axial CT scan with a soft tissue algorithm (b)shows a soft tissue mass (asterisk)isoattenuating to the masseter muscle with additional patches of slight hyperattenuation.Axial T1-weighted image (c)depicts heterogeneous isointense signal intensity with additional patches of interspersed hyperintensity and linear shadow of hypointensity on the mass (asterisk).Axial fat-suppressed T2-weighted image (d)demonstrates a well-defined lesion,which is markedly heterogeneous with linear hypointense septum internally and hypointense peripheral rim surrounding the lesion (asterisk).The bright signal intensity (arrow)due to obstructive sinusitis is demonstrated.Photomicrograph (e)shows that the lesion consists mostly of hemorrhage and necrosis,accompanied by extravasated fibrin and inflamed columnar epithelium (H&E,100).both CT and MR examinations.Seven patients underwent postcon-trast T1-weighted imaging.CT scans were obtained using a standard CT protocol for the paranasal sinuses.Thirteen patients underwent 2.5-mm-thick axial CT scanning with a bone algorithm and all images were reformatted with a soft tissue algorithm without the use of contrast media.In these patients,direct (n =10)or reformatted (n =3)coronal images were also obtained.MR examinations were performed using a 1.5T MR scanner (n =5)(Signa Advantage Horizon;GE Medical Systems,Milwaukee,WI)or a 3.0T MR scanner (n =5)(Signa HDx;GE Medical Sys-tems)with an 8-channel head coil.In these patients,precontrast T1-weighted spin-echo images (n =10)and T2-weighted fast spin-echo images with fat saturation (n =7)or short TI inversion recovery (n =3)were obtained,followed by contrast-enhanced,T1-weightedspin-echo images with fat saturation after the intravenous injec-tion of 0.1mmol/kg of gadolinium dimeglumine in seven patients.Images were obtained in at least two planes with 3mm section thickness and 1mm intersection gap.2.3.Imaging analysisTwo experienced head and neck radiologists retrospectively reviewed all the CT and MR images in consensus.The CT and MR imaging characteristics were analyzed with particular attention to the location,shape (expansile or nonexpansile),size,margin,atten-uation on precontrast CT,changes of the bony walls of the sinonasal cavity on bone CT,signal intensity on precontrast MR,and enhance-ment pattern on contrast-enhanced MR.The attenuation or signal intensity of the lesion was compared with that of the masseterJ.Zou et al./European Journal of Radiology83 (2014) 545–551547Fig.2.Axial CT scan with a soft tissue algorithm(a)shows an irregularly shaped mass in the left maxillary sinus and nasal cavity,which extends to the nasopharynx through choana(asterisk).Coronal CT in a bone algorithm(b)shows an expansile mass located in the enlarged sinus cavity(arrow).The margin is well defined,and the nasal septum is compressed and deformed.There is a large defect in the medial maxillary sinus wall(arrowheads).muscle.The location of each lesion,whether in the maxillary sinus or/and in the nasal cavity,was confirmed according to the site of the main body of the lesion.The size of each lesion was measured at the greatest diameter of the mass.The margin of each lesion was clas-sified as well-defined or ill-defined.On postcontrast MR images, the degree of enhancement was also subjectively assessed as mild enhancement(less than or equal to that of the masseter muscle)or marked enhancement(greater than that of the masseter muscle).3.ResultsThe symptoms of the patients were nasal obstruction in80.0% (12/15),epistaxis in53.3%(8/15),rhinorrhea(n=4),headache (n=3),facial numbness(n=2),visual acuity reduction(n=1), hyposmia(n=3),and syrigmus(n=2).Histopathological examinations showed most of the central areas of the lesion were composed of hemorrhage with exten-sive hyperplastic and dilated thin-walled blood vessels,fibrosis, and thrombus formation,and areas of focal inflammation.The cen-tral areas were surrounded by hemosiderin-laden macrophages, associated with recent hemorrhages(Figs.1e and4d).Grossly,the SAP was seen as a relatively well-circumscribed,lobulated and necrotic mass with a purple or dark red surface that bled easily when touched lightly.On sectioning,the cut surfaces werefirm, alternating with yellow-brown and hemorrhagic necrotic zones that showed cystic degeneration.Moreover,in eight lesions,SAP was found to accompany an inflammatory polyp of the sinonasal cavity.The CT and MR imaging features of the15patients with SAP are summarized in Table1.Eight SAPs occurred in the left side and seven in the right side.Thirteen lesions were located in the maxil-lary sinus and nasal cavity.Two lesions were confined to the nasal cavity.Of these,seven cases extended to the choana and nasophar-ynx(Fig.2).On CT and MR images,these lesions were seen as an expansile mass in10patients(Figs.1a–d,3,and4a–c)and nonexpansile mass infive patients.The size of the lesions ranged from10.4mm to 62.6mm in greatest diameter,with a mean of40.3mm.Thirteen of 15(86.7%)lesions displayed well-defined margins and two of15 (13.3%)lesions were ill-defined(Fig.3b).On CT images,the masses were heterogeneous.The lesions had a soft tissue density andfilled the sinonasal pared with the masseter muscle,the mass was mostly isoattenuated in all patients,with additional patches of slight hyperattenuation in11 patients(Figs.1b and2a).Calcification was not found in any case. Most lesions(12/13)caused changes in the adjacent bone,includ-ing expansile remodeling accompanied by thinning of the bony wall(n=8,Fig.1a),defect or destruction of adjacent bones(n=7, Fig.3a),and hyperostosis of the sinonasal walls(n=6,Fig.3c).The most common site of maxillary wall with expansile remodeling and thinning was the medial wall(n=7),followed by the nasal sep-tum(n=4)and the posterior lateral wall(n=2).The defect of the bony wall also could be seen in the medial wall(n=5),lateral wall (n=3),posterior wall(n=1),and the medial wall of the orbit(n=1). Hyperostosis was seen along the posterior lateral wall(n=5)and the anterior wall(n=3).All of the10lesions examined by MR mostly showed het-erogeneous isointense signal intensity(n=10)on T1-weighted images,with additional points or patches of interspersed slight hyperintensity(n=10)and linear shadow of hypointensity(n=9) (Figs.1c and4a).In contrast,all of the lesions showed markedly het-erogeneous,mixed hyperintense and hypointense signal intensity on T2-weighted images(n=10),with linear hypointense septum internally(n=10)and hypointense peripheral rim surrounding the lesion(n=10)(Figs.1d and4b).Postcontrast MR images demon-strated areas of heterogeneous and marked enhancement(n=7)in all of the lesions with an unenhanced hypointense rim and septa (n=7)(Fig.4c).Obstructive sinusitis was observed in all patients (n=10)in varying degrees(Figs.1d and4b).4.DiscussionThere are numerous descriptions of SAP in the literature, including organized or organizing hematoma[3,7–14],cavernous hemangioma[15–17],hemangioma[18,19],hematoma-like mass of the antrum[20],pseudotumor[21],hemorrhage necrotic polyp, and angioectatic or angiomatous polyp[1,2,4–6,22,23].Study and comparison of these seven terms shows that they all share the same clinical,pathological,and imaging features.The present study uses the term“angiomatous polyp”because it reflects the fact that the lesion is not a real tumor and that the mass is characteristicallyfilled with clusters of irregularly shaped,dilated thin-walled vessels and extensive vascular proliferation.The pathogenesis of SAP has not been elucidated;however, many hypotheses have been proposed.At present,there are two prevailing opinions.One hypothesis is based on the presence of nasal polyps.The polyps are usually located near the sinus ostia and protrude through the sinus ostium into the adjacent cavity. Because of the particular anatomical conditions,the polyp pedicle is subject to significant vascular compromise.Accordingly,the com-pression of the feeder vessels causes stasis,edema,and ischemia of the polyp.This leads to venous infarction followed by neovascular-ization andfibrosis of the polyp,which then evolves into thefinal SAP[23].J.Zou et al./European Journal of Radiology83 (2014) 545–551549Fig.3.Coronal CT scan with bone algorithm(a)shows a soft tissue mass in the left maxillary sinus,which causes a bone defect of the anterior wall(arrow).Coronal CT scan with soft tissue algorithm(b)shows the lesion extends to the fat space and displays an ill-defined margin(arrow).Axial CT scan with bone algorithm(c)demonstrates hyperostosis in the posterior lateral wall of the left maxillary sinus(arrows).Another hypothesis is based on the formation of hematoma in the sinus antrum[3,7,8].The hematoma develops initially from the accumulation of blood in the sinus antrum resulting from various causes,such as trauma,surgery,bleeding diatheses,and the loss of mechanical integrity of an arterial branch,as seen in a ruptured aneurysm or inflammatory erosion of an arterial wall[7,12–14]. The blood remains in the sinus antrum because of poor ventila-tion and drainage conditions,especially in the maxillary sinus.As is known,SAP occurs most frequently in the maxillary sinus,the largest paranasal sinus.These allow conditions of negative pres-sure and decreased ventilation[7].Persistent negative pressure and decreased ventilation lead to difficulties in expelling fresh blood from the maxillary sinus,and subsequently organization and fibrous degeneration of hematoma ensue.Reactive and reparative changes with neovascularization lead to the eventual formation of SAP.This process accounts for the progressive expansion and local bony destruction associated with SAP[3,7,8,13].Based on the results of the present study,the two hypothe-ses are both reasonable.Of the15cases examined,most lesions (n=13)were located near the sinus ostium and often involved the ipsilateral nasal cavity and maxillary sinus through the ostium and extended toward the choana and nasopharynx(n=7).Furthermore, eight cases were associated with the inflammatory polyps proven by pathological reports and/or operative notes.Given these facts, thefirst hypothesis is reasonable in some cases.However,some cases are also consistent with the latter hypothesis.Three cases had a history of previous head and neck surgery or a history of craniofacial trauma.Six cases had a history of frequent epistaxis. Moreover,the most lesions(n=13)were located in the maxillary sinus,and expansion(n=10)and local bony destruction(n=7)were also frequent.A wide age range of patients has been reported,from11to81 years[4,5,14,20,21,24].In the present study,patients’age ranged from12to81years(median,42.7years),and there was a prepon-derance of women,with a male-to-female ratio of1:2.As in the literature[6,7,13,20],patients often presented with nasal obstruc-tion(n=12)and epistaxis(n=8),because gradual enlargement of the lesion displaced the adjacent bony structures and caused inflammatory infiltration of stroma,which eroded the hyperplastic and thin-walled vessels.Reports on of SAP clarified that CTfindings lacked specificity for SAP identification[4,5,7].The typical appearance includes an expansile mass causing bulge or destruction of the bony wall and heterogeneous isoattenuation on precontrast CT scans.The pres-ence of attenuation in the present study is in accordance with the characteristics previously mentioned.In the present study,most of the lesions(n=12)caused changes in the adjacent bone,including expansile remodeling and thin-ning,defect or destruction of adjacent bones,and hyperostosis of the sinonasal walls.Expansile remodeling and thinning of adjacent bones was the most common change(n=8),and may indicate a long growth process and benign growth pattern.In seven cases,defect of the bony wall could also be seen,which was caused by increas-ing pressure and/or bone resorption.Hyperostosis(n=6)may be related to chronic obstructive sinus inflammatory reaction.It is difficult to make accurate diagnoses based only on the CT features,such as the large soft tissue mass with heterogeneous den-sity and the associated bone destruction[1,4].However,the masses are well defined and do not invade the peripheral soft tissue on CT, which is associated with the non-neoplastic growth pattern of SAP. In spite of CT imaging lacking specificity for SAP,it was superior to MR imaging for demonstrating bone changes associated with the lesion.Compared with the CTfindings,the SAP lesion has a char-acteristic appearance on MR images.According to the literature and the present study,the typical imaging features of SAP on550J.Zou et al./European Journal of Radiology 83 (2014) 545–551Fig.4.Axial T1-weighted MR image (a)shows that the lesion is mostly isointense compared to the masseter muscle interspersed with points of hyperintensity (asterisk).Axial,short TI inversion recovery MR image (b)shows the marked heterogeneity of the lesion with a mix of hypointense,and marked hyperintense signals (asterisk).The dark peripheral rim surrounding the lesion is also well demonstrated.The curvilinear hyperintensity area around the mass indicates obstructive sinusitis.Postcontrast axial,fat-suppressed,T1-weighted MR image (c)shows heterogeneous and marked enhancement (asterisk)in most regions of the lesion with an unenhanced hypointense rim and septa.Photomicrograph (d)shows that the lesion consists of hemorrhage,extravasated fibrin,inflamed cells and scattered hemosiderin-laden macrophages (H&E,100×).MR images are as follows:(i)expansive soft tissue mass,(ii)well-defined margin,(iii)blockage of ostium and secondary obstruction,(iv)extension into the choana and nasopharynx,(v)heterogeneous isointense signal intensity with interspersed slight hyperintensity on T1-weighted imaging,and (vi)markedly het-erogeneous,obvious hyperintense with hypointense linear septum internally and peripheral rim surrounding the lesion.Remarkably,the hypointense peripheral rim around the mass is a very specific contribution to the correct diagnosis of SAP.The postcontrast MR images of SAP also demonstrated a char-acteristic appearance with areas of heterogeneous and marked enhancement with unenhanced hypointense rims and septa.In the present study,MR imaging showed the margin and extent of the mass more clearly and more precisely than CT imaging,as reported by Kim et al.[3].The hydrops of the adjacent paranasal sinuses caused by secondary obstruction and inflammation can be differentiated easily from the lesion on MR images,especially on T2-weighted images.However,it is difficult to distinguish between the main lesion and sinus inflammation on CT,which often results in overestimating the size of the lesion.Furthermore,due to the higher soft tissue contrast resolution,MR imaging is superior to CT for determining the internal characteristics of the lesion with var-ious signal intensities on T1-and T2-weighted Images 3.Although an exact 1:1MR-pathologic correlation is not possible because most lesions are removed in pieces and not en bloc,the heterogeneous signal intensity seen on MR images reflects the various components contained within the lesion,such as hemorrhage in various stages,fibrosis,and various amounts of vascular proliferation [3,24].Post-contrast MR imaging can provide valuable information about theblood supply of the mass and the integrity of vessel walls to predict whether a lesion is benign or malignant.As suggested by Lee et al.[7],the areas with enhancement represent the areas of prominent vascular proliferation.Based on previous experience,the appearance of SAP on CT may cause the radiologist to misdiagnose the mass as malig-nant.Bone erosion can also occur in other benign lesions,such as other inflammatory nasal polyps,cholesterol granuloma,fun-gus ball,inverted papilloma and capillary hemangioma [4,7,14,24].The radiologist should not presume that a lesion is malignant simply relying on a defect in the bone on CT images.Contrast enhancement examination is extremely useful,because inflamma-tory polyp,cholesterol granuloma,and fungus ball are not usually enhanced.Inverted papilloma primarily involves the nasal cavity and reveals a characteristic convoluted cerebriform pattern on both T2-weighted imaging and contrast-enhanced T1-weighted imag-ing [25].Capillary hemangioma is difficult to differentiate from SAP both clinically and radiologically.Tubular flow-void signal intensity on both T2-weighted imaging and contrast-enhanced T1-weighted imaging may be a noteworthy contribution to differential diagno-sis [4,26].Malignant tumors demonstrate frank bony destruction,rather than a clearly defined defect of the sinus walls,associated with adjacent tissue invasion,which results in indistinguishable fat space around the lesion [7].For radiologists inexperienced in head and neck pathology,SAP may be misdiagnosed as juvenile nasopharyngeal angiofibroma.The main identifications of juvenile nasopharyngeal angiofibroma as follows:(i)affecting young males,(ii)widening the pterygopalatine fossa with bowing of the poste-rior wall of the maxillary sinus,(iii)multiple flow-void channelsonJ.Zou et al./European Journal of Radiology83 (2014) 545–551551MRI and(iv)marked enhancement after Gd-DTPA administration [2,27].5.ConclusionsCorrect preoperative diagnosis is important for determining therapeutic schedules,because SAP is usually curative with com-plete surgical resection by endoscopic sinus surgery.CT and MR imaging have respective advantages in the diagnosis of SAP.Pre-operative CT images that show the changes in adjacent bones can provide an accurate basis for the determination of the surgical scope.Preoperative MR images that show the characteristic appear-ance in signal intensity can provide an accurate diagnosis of SAP. Therefore,combined application of CT and MR examinations is nec-essary for patients with suspected SAP.Moreover,the characteristic appearance on postcontrast MR images of SAP also provides the basis for qualitative diagnosis and preoperative preparation. 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