Inflammatory pseudotumor is characterized by in- flammatory masses which mimic true neoplastic processes. Histologic findings are predominantly of plasma cells and other elements supported by fibrous stroma (1). The masses may be the results of overre- sponse to a variety of insults of external origin, with al- tered normal immune response (2). Many cases involv- ing the lungs, liver, stomach, and retrorectal spaces,have been reported in the literature(3-6), but to the best our knowledge, this is the first description of in- flammatory pseudotumor involving the anal sphincter complex and demonstrated by ultrasonography and en- dorectal MR imaging.
Case Report
A 37-year-old female presented with a 6-month histo- ry of right perianal mass. Physical examination revealed a soft, non-tender mass in the right perianal region. She denied any history of perianal abscess, fistula or trau- ma. The laboratory findings, including tumor markers, were all within normal limits. Transperineal sonogra- phy showed a well-marginated ovoid heterogeneous low echoic mass, approximately 6x4 cm size, intermin- gled with sparse echogenic foci and involving the anal sphincteric region. In addition, a few spots of flow sig- nal were demonstrated by color flow imaging (Fig. 1.A).
Using a 0.5-T system (Gyroscan T5-II, Philips Medical System, Best, The Netherlands) with body and endorec- tal coils, MR imaging was performed. On T1-weighted axial images, the mass emitted an intermediate signal compared with that of the adjacent gluteus muscle, which had thin septation (not shown). No evidence of ischioanal space infiltration was noted. On T2-weighted
J Korean Radiol Soc 1999;40:7 33- 7 3 5
I n f l a m m a tory Pseudotumor of the Anal Sphincter C o m p l ex : A Case Re p o r t1
Sang Hoon Lee, M.D., So Lyung Jung, M.D., Myeong Im Ahn, M.D., Jee Young Kim, M.D., Young Ha Park, M.D.
We describe a case of inflammatory pseudotumor involving the anal sphincter com- p l ex, and its ultrasonography and MR imaging features. Transperineal ultrasonogra- p hy showed a well-marginated ovoid low echoic lesion intermingled with sparse e- chogenic foci within the right anal sphincter complex. The lesion was of intermediate signal intensity on T1-weighted images and of heterogeneous hyperintensity on T2- we i g h t e d, compared to surrounding muscle. After the infusion of gadolinium, the le- sion showed heterogeneous enhancement, with a multifocal non-enhanced center.
T 2 - weighted endorectal MR images were more accurate in depicting the lesion and anal sphincter complex, and the patient underwent surgical resection. The final histo- logic diagnosis was inflammatory myofibroblastic tumor.
Index words :A n u s, abnormalities A n u s, US
Magnetic resonance(MR), intracavitary coils
1Department of Diagnostic Radiology, St. Vincent Hospital, The Catholic University of Korea, #93 Chi-Dong, Paldal-ku, Suwon, Kyunggido, 442- 723, Korea
Received November 4, 1998 ; Accepted December 30, 1998
본 논문은 1 9 9 9년도 가톨릭중앙의료원 학술연구보조비로 이루어진 것임.
Address reprint requests to : Sang Hoon Lee, M.D. Department of Diagnostic Radiology, St. Vincent Hospital, The Catholic University of K o r e a .
#93 Chi-Dong, Paldal-ku, Suwon, Kyunggido, 442-723, Korea Tel. 82-331-240-2210 Fax. 82-331-247-5713
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coronal and axial images obtained using endorectal coil, heterogeneous high signal intensity was noted, with s- cattered low-signal intensity areas (Fig. 1.B,C).
Gadolinium-enhanced axial images showed heteroge- neous thick peripheral enhancement, with a central non-enhanced portion (Fig. 1.D). T2-weighted endorec- tal MR images depicted the relationship between the anal sphincter complex and the lesion more clearly than did body coil images. The patient underwent surgical resection, but total resection could not be achieved due to subtle infiltration of the mass into the anal sphincter muscle bundles. A yellowish lobulated mass was found, and microscopic examination revealed proliferation of
fibroblastic tissue infiltrated by inflammatory cells, pre- dominantly lymphocytes, and plasma cells (Fig. 1.E).
Mitotic activity or cellular atypia were not noted. The fi- nal histologic diagnosis was inflammatory myofibrob- lastic tumor.
D i s c u s s i o n
Inflammatory pseudotumor is a rare histologically be- nign mass characterized by proliferative myofibroblasts, fibroblasts, histiocytes, and, occasionally, plasma cells and lymphocytes(5). Inflammatory pseudotumor has a variety of synonyms, including plasma cell granuloma,
Sang Hoon Lee, et al : Inflammatory Pseudotumor of the Anal Sphincter Complex
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A B C
D E
Fig.1. A . Transperineal color ultrasonogram shows a well-marginated hypoechoic mass intermingled with sparse echogenic areas.
There is a cluster of flow signal at periphery of the mass (arrow).
B , C. Coronal and axial T2 weighted images with endorectal coil show heterogeneous hyperintense signal mass with low signal foci (curved arrows).
Two halves of the external anal sphincter (black arrowheads), puborectalis muscle (white arrows), and levator ani muscle (black arrows) in normal left side are clearly depicted. Ischioanal spaces (black open arrows) are not involved.
D . Gadolinium-enhanced T1 weighted axial image shows heterogeneously enhancing mass with non-enhancing center (arrow- heads). Note the caudal part of the external anal sphincter (black arrows), internal anal sphincter (white arrows), and urethra (white open arrows) anteriorly.
E . Histologic section of the mass shows spindle cell (fibroblastic tissue) proliferation(white arrows) intermixed with lymphocytes and plasma cells(white arrowheads, Hematoxylin-eosin stain, ×2 0 0 ) .
inflammatory myofibroblastic tumor, histiocytoma, x- anthoma, fibroxanthoma, xanthogranuloma, plasma cell tumor, fibrous xanthoma, xanthematous pseudotu- mor, and plasma cell histiocytoma complex (7). In some cases, there is a history of trauma, surgery, or infection (2). This patient, however, had no history of previous in- sults. The imaging findings of inflammatory pseudotu- mor are non-specific and often resemble true neo- plasms. Previous reported MR findings of retrorectal in- flammatory pseudotumor showed an intermediate sig- nal on T1-weighted images and a heterogeneous in- creased signal on T2-weighted, with obliteration of the adjacent fat plane (6). Although in our case signal inten- sity was similar to that shown by a retrorectal inflam- matory pseudotumor, there were some differences. Our case was well-confined within the anal sphincter com- plex and adjacent ischioanal fat space was well-pre- served. We presumed that these salient features are due to the relatively tight muscle bundles of the anal sphinc- ter complex and the slow growth shown by the tumor.
The low signal intensity foci within the mass, as seen on T2-weighted images, can be explained by the fibrous components of the tumor. After the infusion of gadolini- um, these low signal intensity portions were diffusely enhanced, and non-enhanced focal areas remained, and this suggests a tumor with a more compact fibrous com- ponent, rather than necrosis. A longer delay time might have produced a more completely enhanced lesion.
Recent studies using an endoanal coil have demonstrat- ed the advantage of high spatial resolution and in- creased signal-to-noise ratio for imaging the anal sphinc- ter (8). In our case, using an endorectal coil, anatomical structures including the external anal sphincter, pub-
orectalis muscle, levator ani muscle, and ischioanal space were clearly demarcated. In conclusion, we have described a case of inflammatory pseudotumor with in- volvement limited entirely to the anal sphincter com- plex. The role of endorectal MR imaging was redefined;
this clearly depicted the lesion and surrounding anal sphincter complex, and their appropriate margins, thus permitting the avoidence of unnecessary surgical resec- tion of this complex.
R e f e r e n c e s
1. Hata Y, Sasaki F, Matuoka S. et al. Inflammatory pseudotu- mor of the liver in children : Report of cases and review of the literature. J Pediatr Surg 1992 ; 27 : 1549-1552
2. Freud E, Bilik R, Yaniv I. Et al. Inflammatory pseudotumor in chilhood : A diagnostic and therapeutic dilemma. Arch Surg 1991 ; 126 : 653-655
3. Agrons GA, Rosado-de-Christenson ML, Kirejczyk WM. et al.
Pulmonary inflammatory pseudotumor : Radiologic features.
Radiology 1998 ; 206 : 511-518
4. Abehsera M, Vilgrain V, Belghiti J. et al. Inflammatory pseudotumor of the liver : Radiologic-pathologic correlation. J Comput Assist Tomogr1995 ; 19 : 80-83
5. Taatuta E, Krinsky G, Genega E. et al. Pediatric inflammatory pseudotumor of the stomach : Contrast-enhanced CT and MR imaging findings. AJR 1996 ; 167 : 919-920
6. Georgia JD, Lawrence DP, DeNobile JW. Inflammatory pseudotumor in the retrorectal space : CT and MR appear- ance. J Comput Assist Tomogr 1996 ; 20 : 410-412
7. Matsubara O, Tan-Liu NS, Kenney RM. Et al. Inflammatory pseudotumor of the lung : Progression from organizing pneu- monia to fibrous histiocytoma or to plasma cell granuloma in 32 cases. Hum Pathol 1988 ; 19 : 807-814
8. Hussain SM, Stoker J, Lameris JS. Anal sphincter complex : Endoanal MR imaging of normal anatomy. Radiology 1995 ; 197 : 671-677
J Korean Radiol Soc 1999;40:7 33- 7 3 5
항문 괄약근내의 염증성 가성종양 : 1예 보고1
1가톨릭대학교 성빈센트병원 진단방사선과
이상훈・정소령・안명임・김지영・박영하
항문 괄약근에서 생긴 염증성 가성 종양 1예의 초음파 및 경직장 자기공명 영상 소견을 보고한다. 경회음부 초음파상 우측 항문 괄약근내에 경계가 좋은 타원형의 저에코 병소가 약간의 고에코 병소와 섞여 있었다. 자기 공명영상에서 병변은 T1 강조영상에서 근육과 비교해서 중등도의 신호강도, T2 강조 경직장 자기공명영상은 병 변과 항문 괄약근과의 관계를 명확히 나타내었다. 환자는 외과적 절제술을 시행하였고 조직학적 진단은 염증성 근섬유아세포 종양이었다.
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