An inflammatory myofibroblastic tumor (IMT), or in-flammatory pseudotumor, is a relatively rare quasineo-plastic lesion consisting of inflammatory cells and my-ofibroblastic spindle cells. The exact etiology of an IMTis unknown and whether an IMT represents a reactiveor neoplastic process remains unclear. An IMT was ini-tially described in the lung, but it has subsequently beenfound to potentially involve nearly all areas of the body(1-3). An IMT usually presents as a single mass withina single organ or sometimes as multifocal lesions withina single anatomic region. An IMT involving noncontigu-ous multi-organs is extremely rare (4, 5).

We present a case of an aggressive IMT that involvesmultiple organs within different anatomic regions.

Case Report

A 68-year-old man presented with a one-week historyof right lower extremity weakness and lower back pain.The patient had no trauma history. The laboratory datarevealed only a mild elevation of ESR (18 mm/hr) and aminor degree of thrombocytosis with a platelet count of525,000 platelets/μl. MR imaging showed irregular bonydestructive soft tissue masses involving the body andright pedicle of the L2 vertebra, with expansion to theepidural space and the ipsilateral neural foramen (Fig.1A-C). Since the lesion was considered a metastasis, weperformed a diagnostic work-up to find the primary ma-lignancy. A contrast-enhanced abdominopelvic CT scandemonstrated the presence of multiple nodules in thespleen, both kidneys, pancreas, right paravertebral, andbladder wall (Fig. 1D-H). From brain MR imaging, a1.5 cm, well enhanced mass was noted that extendedfrom the hypothalamus to the pituitary stalk.

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Non-contiguous Multi-organ Involvement of anInflammatory Myofibroblastic Tumor: A Case Report1

Jae-Wook Lee, M.D., Ki Whang Kim, M.D. , Kyung-Mi Paek, M.D., Mi-Suk Park, M.D., Jae-Yeon Seok, M.D.2, Sungjun Kim, M.D.3, Myeong-Jin Kim, M.D.

1Department of Diagnostic Radiology, Yonsei University College ofMedicine, Research Institute of Radiological Science, Yonsei UniversityCollege of Medicine

2Department of Pathology, Yonsei University College of Medicine 3Department of Diagnostic Radiology, Hanyang University MedicalCenterReceived April 12, 2006 ; Accepted August 2, 2006Address reprint requests to : Ki Whang Kim, M.D., Department ofDiagnostic Radiology, Severance Hospital, Seodaemun-gu, Shinchon-dong 134, Seoul 120-752, Republic of KoreaTel. 82-2-2228-7400 Fax. 82-2-393-3035E-mail: kwkimyd@yumc.yonsei.ac.kr

An inflammatory myofibroblastic tumor (IMT) is relatively rare quasineoplastic le-sion. An IMT usually presents as a single mass within a single organ or sometimes asmultifocal lesions within a single anatomic region. An IMT involving noncontiguousmulti-organs within different anatomic regions is extremely rare. We present a case ofan aggressive IMT that involved the musculoskeletal system and multiple abdominalvisceral organs.

Index words : Computed tomography (CT)Magnetic resonance (MR), image display Abdomen, CTSpine, MR

The patient underwent an excisional biopsy for the le-sion in the L2 vertebra. An microscopic examination re-vealed diffuse dense collagenous fibrosis admixed withintervening, mature looking lymphoid cells and plasmacells, which is consistent with an IMT (Fig. 1I, J). An ad-ditional ultrasound-guided biopsy of the splenic mass re-vealed the same microscopic findings as the L2 vertebrallesion, therefore enabling the conclusion of the same di-agnosis of an IMT. Thirteen months after discharge, thepatient received a follow-up abdominopelvic CT andbrain MRI. A contrast enhanced CT scan showed a de-crease in the size of the nodules in the spleen, and noresidual masses were noted in the kidneys and pancreas(Fig. 1K, L). From the brain MRI, no mass was demon-strable in the hypothalamic area.

Discussion

An inflammatory myofibroblastic tumor, also known

as an inflammatory pseudotumor, is defined as “a tumorcomposed of differentiated myofibroblastic spindle cellsusually accompanied by numerous plasma cells and/orlymphocytes” by the 1994 WHO Classification of SoftTissue Tumors (6). Coffin et al. (1) subdivided this raretumor type into three histological subtypes: myxoid-vas-cular, hypocellular fibrous, and the compact spindle celltype. The tumor mainly affects young patients and mostoften involves the lung and the orbit, but may occur invirtually any anatomic location and at any age.

Whereas the exact etiology of an IMT is unknown, anIMT has been thought to result from inflammation fol-lowing trauma, surgery, or acute infection. Other inves-tigators argue that an IMT is a true neoplastic lesion.Some IMT cases with malignant transformation ormetastasis to distant organs have been demonstrated inthe literature (2). There are only sporadic descriptions ofthe radiological findings for IMT in the medical litera-ture and the reported findings are variable depending on

Jae-Wook Lee, et al : Non-contiguous Multi-organ Involvement of an Inflammatory Myofibroblastic Tumor

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A B

C

Fig. 1. A-C. MR imaging demonstrates the mass destroying theL2 vertebral body and the right pedicle, and expanding to theepidural space and the neural foramen. The mass shows hetero-geneous hypo- and hyperintensity on the axial T2-weighted im-age (A) and isointensity on the T1-weighted image (B). The post-contrast T1-weighted image (C) reveals a well-enhanced lesion.

the involved organ, histological subtype, and are eveninconsistent within the same organ (3, 4).

IMT bone involvement is extremely rare, and the gen-eral imaging features of this involvement have not beenwell described (7, 8). In our case, a bony lesion demon-

strated heterogeneous signal intensity on T2WI, homo-geneous iso-signal intensity on T1WI, and heteroge-neously well-enhanced intensity on gadolinium-en-hanced T1WI with expansion to the epidural space andthe neural foramen. These findings cannot be differenti-

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D E

F G

H

Fig. 1. D-H. Contrast enhanced CT images show variable-sized,multiple, hypodense masses (arrows) in the spleen (D, E), pan-creas head (F), right kidney (F), left kidney (G), right paraverte-bral area (G), and bladder wall (H).

ated from a metastasis or other primary bone tumors.The MR findings of IMT may be low to intermediate sig-nal intensity on T1- and variable signal intensity on T2-weighted images and possible strong enhancement withgadopentetate dimeglumine (3). Han et al. (9) suggestedthat the T2 hypointensity of a soft-tissue lesion might beexplained by a relative lack of both free water and mo-bile protons within the fibrotic lesions. Hoger et al. (4)reported a case of synchronous IMTs with different sub-types. In that case, the MRI signal on T2-weighted se-quence was lower in the spindle cell variant than that inthe myxoid-vascular subtype, but reliable differentiationby MRI was not possible. Therefore, MR signal intensi-ties may differ according to histological subtype and/orthe degree of inflammation as well as the amount of fi-brotic content within the tumor.

An IMT has been reported in various sites within theabdomen, including the liver, spleen, pancreas, adrenalgland, kidney, retroperitoneum, diaphragm, mesentery,and the alimentary and urinary tracts. An IMT has avariable CT appearance. On un-enhanced scans, themass may be hypoattenuated or isoattenuated relative tothe muscle, with or without calcification. Enhancementwith contrast material administration frequently occursand is not pronounced and a variety of patterns hasbeen noted. These patterns include early peripheralwith delayed central filling, heterogeneous, homoge-neous, and no enhancement. Larger lesions may havecentral necrosis (3). In our case, the spleen was patho-logically proven as the intra-abdominal organ that theIMT involved. However, considering follow-up imagingfindings that showed marked regression of the lesions,

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I J

K LFig. 1. I, J. Diffuse, dense collagenous fibrosis admixed with intervening, mature looking lymphoid cells and plasma cells, whichare consistent with IMT histology (H & E staining, I: ×40, J: ×400). K, L. Follow-up contrast enhanced CT images show a decrease in the size of the masses (arrows) in the spleen (K), left kidney (L),and pancreas (L).

we assume that the IMT also involved the kidneys, pan-creas, paravertebral area, bladder wall, and brain. In ad-dition, all of the lesions involving the intra-abdominalorgans were homogeneous iso- or hypo-attenuatedmasses relative to the muscle on contrast-enhanced CT.The density and enhancement patterns of this case weresimilar to those described in previous reports. However,the radiological findings in this case were nonspecificand the lesions could not be differentiated from a lym-phoma, melanoma, or other metastatic or multi-organinvolved lesions.

In conclusion, this case certifies that this rare entitymay demonstrate non-contiguous, multi-organ involve-ment, aggressive growth patterns, and variable signal in-tensities. In addition, this case shows inconsistent en-hancement with MR and CT imaging. Therefore, whendealing with such cases, an IMT should be included as apotential differential diagnosis, even though these casesare very rare.

References

1. Coffin CM, Watterson J, Priest JR, Dehner LP. Extrapulmonary in-flammatory myofibroblastic tumor (inflammatory pseudotumor).

A clinicopathologic and immunohistochemical study of 84 cases.Am J Surg Pathol 1995;19:859-872

2. Dehner LP. The enigmatic inflammatory pseudotumours: the cur-rent state of our understanding, or misunderstanding. J Pathol2000;192:277-279

3. Narla LD, Newman B, Spottswood SS, Narla S, Kolli R.Inflammatory pseudotumor. Radiographics 2003;23:719-729

4. Horger M, Pfannenberg C, Bitzer M, Wehrmann M, Claussen CD.Synchronous gastrointestinal and musculoskeletal manifestationsof different subtypes of inflammatory myofibroblastic tumor: CT,MRI and pathological features. Eur Radiol 2005;15:1713-1716

5. Di Vita G, Soresi M, Patti R, Carroccio A, Leo P, Franco V, et al.Concomitant inflammatory pseudotumor of the liver and spleen.Liver 2001;21:217-222

6. Weiss SW. Histological Typing of Soft Tissue Tumours. 2nd ed. Berlin:Springer-Verlag, 1994

7. Sciot R, Dal Cin P, Fletcher CD, Hernandez JM, Garcia JL, SamsonI, et al. Inflammatory myofibroblastic tumor of bone: report of twocases with evidence of clonal chromosomal changes. Am J SurgPathol 1997;21:1166-1172

8. Allanore Y, Pham XV, Clerc DA, Menkes CJ, Kahan A. Sacral in-flammatory pseudotumor revealed by paraneoplastic syndrome.Rheumatol Int 2004;24:166-168

9. Han MH, Chi JG, Kim MS, Chang KH, Kim KH, Yeon KM, et al.Fibrosing inflammatory pseudotumors involving the skull base:MR and CT manifestations with histopathologic comparison.AJNR Am J Neuroradiol 1996;17:515-521

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대한영상의학회지 2007;57:265-269

비연속적으로 다수의 장기에 발생한 염증성 근섬유모세포성 종양: 증례 보고1

1연세대학교 의과대학 영상의학과2연세대학교 의과대학 병리학교실3한양대학교 의과대학 영상의학과

이재욱·김기황·백경미·박미숙·석재연2·김성준3·김명진

염증성 근섬유모세포성 종양(inflammatory myofibroblastic tumor)은 상대적으로 드문 유사신생물로 일반적으로

단일 장기에 단일 병변, 또는 가끔 단일 해부학 영역에서 다수 병변으로 발견된다. 하지만, 다른 해부학적 영역에서

비연속적으로 다수의 장기에서 발생하는 경우는 매우 드물다. 이에 저자들은 근골격계와 다수의 복강 내 장기에 발

생한 염증성 근섬유모세포성 종양의 증례를 보고한다.