Inflammatory Myofibroblastic Tumor of the Small Bowel Mesentery Mimicking Ectopic Pregnancy

May 25, 2007
Surgical Rounds®, January 2006, Volume 0, Issue 0

Ali Elhorr, Resident in General Surgery, Department of Surgery, North Oakland Medical Centers, Pontiac, MI, Wayne State University, Detroit, MI; Ehab Elakkary, Resident in General Surgery, Department of Surgery, North Oakland Medical Centers, Pontiac, MI, Wayne State University, Detroit, MI; Wissam Bleibel, Resident in Family Practice, Department of Family Practice, North Oakland Medical Centers, Pontiac, MI; Thanh Phan, Staff Surgeon, North Oakland Medical Centers, Pontiac, MI

Ali Elhorr, MD

Resident in General Surgery Department of Surgery North Oakland Medical Centers Pontiac, MI Wayne State University Detroit, MI

Ehab Elakkary, MD

Resident in General Surgery Department of Surgery North Oakland Medical Centers Pontiac, MI Wayne State University Detroit, MI

Wissam Bleibel, MD

Resident in Family Practice Department of Family Practice North Oakland Medical Centers Pontiac, MI

Thanh Phan, MD

Staff Surgeon Department of Surgery North Oakland Medical Centers Pontiac, MI

Inflammatory myofibroblastic tumors belong to a rare class of pseudosarcomatous inflammatory lesions that are usually benign and nonmetastasizing, but have a tendency to recur. These tumors originate as a mass in the soft tissue and viscera and are found mainly in children and young adults. The lungs are the most common site of occurrence.1 Extra?pul?monary sites include the mesentery, omentum, and, to a lesser extent, the liver, spleen, esophagus, and lymph nodes. Although its etiology remains unknown, some attribute these tumors to an inflammatory response, because evidence of infection with the Epstein-Barr virus is often present, whereas others consider these lesions a neoplastic process with the potential for malignant transformation.

Case report

A 20-year-old woman who was 4 weeks pregnant (gravida 2, para 1) presented to the emergency department with right lower quadrant abdominal pain of 2 days duration. The pain was described as dull, increasing with activity, but not radiating. The patient reported no weight loss, fever, anorexia, vaginal bleeding, dysuria, or change in bowel habits. On physical examination, she was not in acute distress. No peripheral lymphadenopathy was noted in the head, neck, axillary, or groin. The abdomen was mildly tender in the right lower quadrant with no peritoneal signs on palpation. The rectal e?x?am?ination was normal. Laboratory studies, which included a complete blood count, complete metabolic panel, and vaginal cultures, were normal. Her B-HCG level was normal and corresponded to the gestational age of the embryo.

Abdominal ultrasonography revealed no intrauterine pregnancy, but showed a 5.7-cm, sac-like structure in the right adnexa that was suspicious for ectopic pregnancy. The patient was subsequently taken to the operating room by the gynecology service for a diagnostic lapa-ro?scopy. There were normal fallopian tubes and ovaries bilaterally, but a solid mass was identified on the antimesenteric border of the ileum, which required surgical consultation. An exploratory laparotomy was performed and the mass was found to be smooth, pedunculated, and greenish white in color, measuring 3.2 x 2.5 x 2.5 cm. No other abnormalities were found in the liver, spleen, and pancreas, and there was no lymphadenopathy. About 7 cm of the ileum was transected, including the mass in the mesentery, and a primary end-to-end anastomosis was performed. The ileocecal valve was preserved.

Histologic examination of the mass showed an extensively hyalinized inflammatory myofibroblastic tumor (Figure). Hematoxylin and eosin staining revealed a dense proliferation of spindle cells and inflammation, which resembled granulation tissue. Immunohistochemical staining was positive for cytokeratin, desmin, P53, S100, CD34, CD117, vimentin, and smooth muscle actin. In addition, kappa and lambda light chains were applied to the specimen to demonstrate polyclon-ality in the plasma cell infiltrates that formed the background of this lesion. These features were compatible with an inflammatory myofibroblastic tumor.

The patient's postoperative recovery was uneventful. Her diet was advanced as tolerated until she fully regained bowel function. She was discharged to home on postoperative day 5, but because her erythrocyte sedimentation rates were elevated, she was advised to undergo serial erythrocyte sedimentation rate testing after discharge from the hospital.

Since the operation, the patient has undergone physical examinations and abdominal computed tomography (CT) scans every 6 months. She has also had head and chest CT scans on an annual basis. The patient has been free of local and metastatic disease after 2 years of follow-up.

Discussion

Mycobacterium avium-intracellulare

Pseudosarcomatous inflammatory le?sions are a distinctive type of inflammatory myofibroblastic tumor. These soft tissue tumors have been reported mainly in children and young adults. Most in?flammatory myofibroblastic tumors have been reported in the lungs.1 A wide variety of terminology has been used to describe these lesions, including plasma cell pseudotumor, xanthomatous pseudotumor, plasma cell granuloma, pseudo?sar?comatous myofibroblastic proliferation, inflammatory myofibrohistiocytic pro??life?ra?tion, and, most commonly, in?flam?matory pseudotumor.2-4 Inflammatory myofibro-blastic tumor is the preferred term because inflammatory pseudotumor has been ap?plied to many different entities, including reparative pseudosarcomatous lesions of the lower genitourinary tract and infectious lesions, such as those resulting from infection5,6 and follicular dendritic cell tumors associated with the Epstein-Barr virus (usually detected in the liver or spleen).7-10

The mesentery and omentum are the most common sites of extrapulmonary inflammatory myofibroblastic tumor. In a study by Coffin and associates, 43% of these tumors (36 of 84) arose in these sites.11 Extrapulmonary inflammatory myo?fibroblastic tumors show a predilection for children, with a mean age of 10 years at presentation. Females are affected slightly more commonly than males. Presenting symptoms depend on the site of primary tumor involvement. Patients with intra-abdominal tumors usually present with abdominal pain, an abdominal mass with increased girth, or, occasionally, with intestinal obstruction. Some patients have prominent systemic manifestations, including fever, night sweats, weight loss, and malaise. Reappearance of these symptoms usually heralds a recurrence of the tumor. Laboratory ab?normalities are rarely present, but in?clude an elevated erythrocyte sedimentation rate, anemia, thrombocytosis, and hypergammaglobulinemia; these abnormalities often resolve with excision of the lesion.11-15

Inflammatory myofibroblastic tumors in the abdomen and retroperitoneum tend to have a propensity for more aggressive clinical behavior. A report by Sanders and colleagues documented four cases of such tumors of the alimentary tract, one involving the appendix, one in the rectum, one at the gastroesophageal junction, and one involving the sigmoid colon.15 One patient had two recurrences. The first occurred within 2 months and was treated by surgical resection. The second was discovered 6 months later and regressed without surgical intervention while the patient was on oral anti-inflammatory therapy.

In a study of extrapulmonary tumors by Coffin and associates, 29 of 53 cases underwent follow-up, with 13 of these patients (25%) having one or more recurrences over a period of 24 months after the initial excision.11 Of these 13 patients, nine had retroperitoneal or intra-abdominal tumors, including two tumors that underwent histologic transformation into higher-grade sarcomas. None of the pa?tients who were followed up developed metastatic disease, including the two who had histologic transformation into higher-grade sarcomas. Two patients with mesenteric tumors died as a direct result of their tumors. Tumors that were more likely to result in aggressive behavior included intra-abdominal or retroperito?neal lesions, tumors that were in close proximity to vital structures, and multi-nodular tumors, all of which compromised complete surgical excision.

It has been accepted that an aberrant response to tissue injury, with myofibro-blast being the primary cell type responsible, can cause inflammatory myofibro-blastic tumors. Evidence of infection with the Epstein-Barr virus has been shown with these lesions.1 Others think inflammatory myofibroblastic tumors are a neoplastic process that have the tendency toward infiltrative local growth and local recurrence. They also tend to become multifocal and noncontiguous tu?mors, with the propensity for vascular invasion and malignant transformation.16

Inflammatory myofibroblastic tumors in the root of the small bowel mesentery need to be differentiated from other space-occupying lesions, such as sarcomas of the mesentery, lipomas, fibromas, retroperitoneal fibrosis, pancreatic cysts, metastatic lesions of the small bowel mesentery from other primaries, and aneurysms of the superior mesenteric artery.12 A CT scan can differentiate a solid mass from a cystic lesion. The final diagnosis, however, usually requires a la?p?arotomy and a pathologic examination of the specimen.

Treatment of inflammatory myofibro-blastic tumors entails surgical removal of the lesion with reexcision of recurrent tumors. There has been one reported case of steroid therapy achieving regression of one such renal tumor, but there has been controversy over the use of nonsteroidal, anti-inflammatory drugs.15 Chemotherapy or radiation is not indicated for these lesions. Given the high local recurrence rate for intra-abdominal tumors and their potential for metastasis, close follow-up with physical examination, radiological imaging, and serial erythrocyte sedimentation rate testing is recommended.

References

1. Cerfolio RJ, Allen MS, Nascimento AG, et al. Inflammatory pseudotumors of the lung. Ann Thorac Surg. 1999;67(4): 933-936.

2. Sculley RE, Mark EJ, McNeely BU. Case records of the Massachusetts General Hospital. Case 13?1984. Cellular inflammatory pseudotumor involving ileal mesentery. N Engl J Med. 1984;310(13): 839-845.

Histopatholo

3. Ramachandra S, Hollowood K, Bisceglia M, et al. In?flam?matory pseudotumour of soft tissues: a clinicopathological and immunohistochemical analysis of 18 cases. gy. 1995;27(4):313-323.

4. Wu JP, Yunis EJ, Fetterman G, et al. Inflammatory pseudotumors of the abdomen: plasma cell granulomas. J Clin Pathol. 1973;26(12): 943-948.

5. Wood C, Nickoloff BJ, Todes-Taylor NR. Pseudotumor resulting from atypical mycobacterial infection: a "histoid" variety of Mycobacterium avium-intracellulare complex infection. Am J Clin Pathol. 1985;83(4):524-527.

6. Umlas J, Federman M, Crawford C, et al. Spindle cell pseudotumor due to Mycobacterium avium-intracellulare in patients with acquired immunodeficiency syndrome (AIDS). Positive staining of mycobacteria for cytoskeleton filaments. Am J Surg Pathol. 1991;15(12):1181-1187.

7. Arber DA, Weiss LM, Chang KL. Detection of Epstein-Barr virus in inflammatory pseudotumor. Semin Diagn Pathol. 1998;15(2): 155-160.

8. Selves J, Meggetto F, Brousset P, et al. Inflammatory pseudotumor of the liver. Evidence for follicular dendritic reticulum cell proliferation associated with clonal Epstein-Barr virus. Am J Surg Pathol. 1996;20(6): 747-753.

Am J Surg Pathol

9. Shek TW, Ho FC, Ng IO, et al. Follicular dendritic cell tumor of the liver. Evidence for an Epstein-Barr virus-related clonal proliferation of follicular dendritic cells. . 1996;20(3): 313-324.

10. Arber DA, Kamel OW, van de Rijn M, et al. Frequent presence of the Epstein-Barr virus in inflammatory pseudotumor. Hum Pathol. 1995;26(10):1093-1098.

11. Coffin CM, Watterson J, Priest JR, et al. Extrapulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor). A clinicopathologic and immunohistochemical study of 84 cases. Am J Surg Pathol. 1995;19(8):859-872.

12. Meis JM, Enzinger FM. Inflammatory fibrosarcoma of the mesentery and retroperitoneum. A tumor closely simulating in?flammatory pseudotumor. Am J Surg Pathol. 1991;15(12):1146-1156.

13. Stringer MD, Ramani P, Yeung CK, et al. Abdominal in?flam??matory myofibroblastic tumours in children. Br J Surg.1992;79(12): 1357-1360.

14. Souid AK, Ziemba MC, Dubansky AS, et al. Inflammatory myofibroblastic tumor in children. Cancer. 1993;72(6): 2042-2048.

15. Sanders BM, West KW, Gingalewski C, et al. Inflammatory pseudotumor of the alimentary tract: clinical and surgical experience. J Pediatr Surg. 2001;36(1):169-173.

16. Coffin CM, Humphrey PA, Dehner LP. Extrapulmonary inflammatory myofibroblastic tumor: a clinical and pathological survey. Semin Diagn Pathol. 1998;15(2):85-101.