Inflammatory Myofibroblastic Tumor of the Small Bowel Mesentery: An Unusual Cause of Abdominal Pain and Uveitis
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- Choi, A.H., Bohn, O.L., Beddow, T.D. et al. J Gastrointest Surg (2011) 15: 584. doi:10.1007/s11605-010-1408-3
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An inflammatory myofibroblastic tumor (IMT) of the small bowel mesentery with diffuse immunohistochemical staining for the anaplastic lymphoma kinase 1 gene is reported in a patient who presented with abdominal pain and uveitis.
To our knowledge, only seven cases of IMT affecting the small bowel mesentery have previously been reported in the English literature. The association of IMT and uveitis is a rare phenomenon, previously reported in patients with IMT affecting the head and neck. Surgical resection of the IMT resulted in rapid resolution of the uveitis.
IMT should be considered in the differential diagnosis for a mesenteric mass.
Inflammatory myofibroblastic tumor (IMT) is an uncommon neoplasm first described in the lung1 and originally thought to occur predominately in pediatric patients. Extrapulmonary IMTs have also been described in the liver,2 spleen,3 mesentery,4,5 head and neck,6,7 heart,8 and retroperitoneum.9 IMTs have also been reported in patients of all ages ranging from neonates to the elderly. Although IMT was originally felt to be reactive in origin, growing evidence suggests that it is a true neoplasm with the potential for invasion of surrounding structures, local recurrence, and distant metastases.10 Up to half of patients with IMTs have a chromosomal abnormality in the anaplastic lymphoma kinase (ALK) 1 gene on chromosome 2p23 resulting in the activation of a tyrosine kinase receptor that is normally expressed only in neural tissue.11 Recent studies have attempted to correlate the presence of ALK 1 gene expression with local recurrence, distant metastases, and overall prognosis in patients with IMT.
Patients with IMTs most commonly present with pain. They may also present with a syndrome of fatigue, anemia, and weight loss.10 The pathophysiology of IMT remains unclear, although inflammatory, infectious, and neoplastic mechanisms have been suggested as potential etiologic factors. Similar to retroperitoneal fibrosis, IMT has been reported in conjunction with other autoimmune diseases and/or symptoms.12 Herein, we report the eighth case of a mesenteric IMT in the English literature4,5,13–17 in a patient presenting with abdominal pain, fatigue, weight loss, uveitis, and anemia.
A 34-year-old Latino man presented with a 2-month history of intermittent, crampy periumbilical and left-sided abdominal pain and a 1-year history of intermittent low back pain. In addition, he developed photophobia and his eyes became red and painful. A complete review of systems was significant for fatigue, diaphoresis, weight loss, and palpitations. He denied associated anorexia, nausea, vomiting, change in bowel habits, melena, or hematochezia.
His past medical history was significant for two seizures at the age of 18 and a transient ischemic attack at age 29. His physical exam revealed marked conjunctival injection bilaterally. He had a nondistended abdomen that was soft and nontender with no palpable masses.
An exploratory laparotomy revealed a solid mass in the small bowel mesentery just beyond the takeoff of the main trunk of the superior mesenteric artery with inflammatory changes extending into the mesentery of the right colon and adjacent enlarged mesenteric lymph nodes. The small and large bowel were normal in appearance and palpation. There were no liver or peritoneal metastases.
On postoperative day 1, the patient had a low-grade fever, tachycardia, and a witnessed seizure. A neurological evaluation and computed tomography of the head were negative. The rest of his postoperative course was unremarkable. He was discharged on postoperative day number five and was seen in follow-up 1 week later with resolution of his eye pain and photophobia and marked improvement in his conjunctival injection. A diagnosis of anterior uveitis was made on a postoperative ophthalmologic exam and he was started on steroid eye drops. The patient returned for ophthalmology follow-up 1 month after surgery and his uveitis had resolved and his steroid eye drops were discontinued.
IMT is classified by the World Health Organization as a neoplasm of intermediate biologic potential because of its potential for invasion of surrounding structures and development of local recurrence and distant metastases.18,19 IMT has also been variously referred to as inflammatory pseudotumor, plasma cell granuloma, pseudosarcomatous myofibroblastic lesion, and inflammatory myofibrohistiocytic lesion. IMT is characterized by spindle cell proliferation in a variable background of inflammatory cells.18 A benign IMT cannot be differentiated from a malignant tumor based on radiographic appearance alone. In a mesenteric location, the differential diagnosis includes lymphoma, sarcoma, desmoid tumor, carcinoid tumor, and a gastrointestinal stromal tumor.4
The characteristic pathologic and molecular features of IMT help distinguish it from other mesenteric tumors.10 IMTs are characterized by uniform-appearing spindle cells which on ultrastructural examination are predominately myofibroblasts and, to a lesser extent, fibroblasts. IMTs are positive for smooth muscle actin in 80–90% of cases, express desmin in 60–70% of cases, and have focal keratin reactivity in one third of cases.10 The spindle cells are present within a background of inflammatory cells, mainly plasma cells, lymphocytes, and eosinophils. Approximately 50% of IMTs are positive for ALK 1 on immunohistochemistry whereas most tumors considered in the differential diagnosis of an IMT in the small bowel mesentery are ALK 1-negative.10
The etiology of IMT is unknown. IMTs have been reported in association with infectious agents,20,21 trauma, surgery,22 autoimmune disease, and most recently with chromosomal abnormalities in the ALK 1 gene. IMT has been reported in patients with a variety of autoimmune diseases, including rheumatoid arthritis,2,23 systemic lupus erythematosus,24 Sjögren’s syndrome,25 and adult-onset Still’s Disease.26 The associated fever, weight loss, anemia, and fatigue that were seen in our patient with IMT and reported by others seem to be related to the effects of proinflammatory cytokines, similar to other chronic inflammatory and autoimmune disorders.2 The potential for immune-mediated phenomena is particularly relevant in our patient who had concomitant uveitis. Reports of IMT with associated uveitis are rare, and the handful of cases in the literature typically involved a primary IMT of the head and neck region.6,7 In those cases, the proximity of the IMT to the eye was thought to account for the development of uveitis. However, uveitis associated with a primary mesenteric IMT suggests the presence of circulating systemic inflammatory cytokines or autoantibodies.
Although intraocular aspiration was not used to definitively establish the etiology of the uveitis in our patient, we suspect that the uveitis was a systemic manifestation of the mesenteric IMT. The onset of ocular symptoms occurred in association with the onset of the abdominal pain. Additionally, the patient experienced marked improvement in his scleral injection and resolution of his photophobia and eye pain less than 2 weeks following resection of the IMT. One week after hospital discharge, he was examined by an ophthalmologist and was diagnosed with uveitis, similar to what is seen with other autoimmune disorders and was treated with ocular steroids. It is conceivable that the uveitis may have resolved completely after tumor excision without any other intervention.
Advances in molecular pathology have demonstrated that up to one half of all IMTs have mutations in the ALK1 gene,27 a gene that was first identified in association with anaplastic large cell lymphoma. The presence of chromosomal abnormalities, local recurrence, and distant metastases4,28,29 establish that IMT is a true neoplasm. Researchers are currently investigating whether ALK 1 tumor positivity is predictive of tumor behavior and prognosis. In a series of 59 cases of IMT selected for histologic atypia or tumor aggressiveness, Coffin et al. reported that 56% were ALK 1-positive. ALK 1-positive tumors were more common in younger patients and patients with local recurrence. Metastatic disease was limited to ALK 1-negative tumors.27 As a result, we have chosen to follow our patient with a yearly computed tomogram of the abdomen to evaluate for recurrence. Although other groups have reported that ALK 1-positive tumors are associated with improved prognosis,28,30 the relationship between ALK 1 positivity and IMT prognosis has not been definitively established.
A complete en bloc resection of the tumor is the mainstay of therapy. Chemotherapy with or without radiotherapy has been used for patients with incomplete tumor resection, positive margins, tumors not amenable to resection, and metastatic disease despite lack of definitive data establishing the efficacy of adjuvant therapy. Adjuvant chemotherapy regimens that have been reported include vincristine or vinorelbine with methotrexate,31,32 ifosfamide regimens with carboplatin or doxorubicin32,33 and imatinib.33 Corticosteroids have been used as a primary form of treatment for IMT with demonstrated tumor regression34,35 and also as an adjunct to reduce inflammation and swelling of surrounding tissue in patients with IMTs involving the central nervous system.32 Radiotherapy has been demonstrated to have some benefit, mainly in pulmonary IMT.36–38 There is currently no evidence that chemotherapy or radiotherapy have a role for patients following complete resection. Despite the frequently reported use of adjuvant therapy for IMT in the literature, there is no definitive data establishing that it is efficacious and there are no standardized treatment protocols.32
Butrynski and colleagues have recently reported the use of crizotinib, an ALK tyrosine kinase inhibitor, for the treatment of IMT. One patient with an IMT positive for ALK rearrangement demonstrated sustained partial response after surgical resection and crizotinib therapy, but another patient with ALK-negative IMT did not respond to crizotinib after tumor debulking.33 For the subset of IMT patients with ALK rearrangements, ALK tyrosine kinase inhibitors represent a potential promising modality for targeted neoadjuvant or adjuvant therapy for locally invasive, incompletely resected, locally recurrent, and unresectable tumors.