Inflammatory myofibroblastic tumor of the small intestine ...



Inflammatory myofibroblastic tumor of the small intestine: A case report

Jun-Xia Li 1*, Pei-You Gong2*, Jun-sun3, Yong-Bin Lv2, Jie-Liu 3, Feng-Li Liu2, Hai-Zhu Xie2

1.Department of Oncology, Yantai Yuhuangding hospital, 20# Yuhuangdingdong Road,Yantai 264000, Shandong Province,PR China.

2.Department of Radiology, Yantai Yuhuangding hospital, 20# Yuhuangdingdong Road,Yantai 264000, Shandong Provin ce,PR China.

3.Department of Biochip-laboratory, Yantai Yuhuangding hospital, 20# Yuhuangdingdong Road,Yantai 264000, Shandong Province,PR China.

*Contributed equally

Correspondence to: Dr Pei-You Gong or Dr Jun-sun , Department of radiology or biochip-laboratory, Yantai Yuhuangding hospital, 20# Yuhuangdingdong Road,Yantai 264000, Shandong Province,PR China.

E-mail: gongpeiyou1970@

E-mail: 1986sunjun@

Telephone: +86-0535-6691999

Jun-Xia Li: lijunxia1972@;

Pei-You Gong: gongpeiyou1970@;

Jun-sun ：1986sunjun@

Yong-Bin Lv：lvyongbin1976@

Jie-Liu ：liujie1977@

Feng-Li Liu: liufengli1957@

Hai-Zhu Xie ：xiehaizhu1965@

Abstract

Inflammatory myofibroblastic tumors (IMTs) are rare lesions of low malignant potential consisting of inflammatory cells inside a mesenchymal stroma comprising myofibroblasts. Here we describe a case of IMT in a 15-year-old girl .The contrast-enhanced CT scan showed uneven arterial enhancement, delayed lesion enhancement, blood supply to the mass via branches of superior mesenteric artery, and obviously enhanced nodules (some with central necrosis) in the mesentery. These CT findings may provide new clinical insights for the differential diagnosis of tumors of the small intestine.

Keywords: inflammatory myofibroblastic tumor, small intestine, computed tomography, radiographic image enhancement, anaplastic lymphoma kinase

Background

Inflammatory myofibroblastic tumor (IMT) is a general term recently applied to rare, low-grade tumors characterized by myofibroblastic proliferation and inflammatory infiltration. This tumor is now recognized as a distinct neoplastic process with specific molecular alterations. Treatment is based on tumor status[1]. IMTs have been reported in multiple locations including the lung, liver, spleen, stomach, abdominal cavity, omentum, retroperitoneum, orbit, spinal meninges, heart, thyroid gland, and kidney; however, most IMTs are located in the lungs, and IMTs are the most common pulmonary tumor of childhood. Extrapulmonary IMTs typically affect younger patients (first and second decades), in contrast with a peak incidence in mid-adulthood for the pulmonary IMTs[2].

Here we report a case of IMT in the small intestine in a 15-year-old girl. The specific enhancement pattern of the tumor and surrounding metastatic nodules on computed tomography (CT) imaging may provide new clinical insights for the preoperative diagnosis of small intestine tumors.

Case presentation

The 15-year-old girl was admitted to the local hospital after experiencing abdominal pain without obvious cause that had increased over the previous 2 days. She experienced abdominal distension and mild but continuous periumbilical pain that did not radiate elsewhere, along with nausea and vomiting. The vomitus was greenish yellow fluid similar to bile. The stool was dark brown, and abdominal pain did not decrease after defecation. The patient received a transfusion for acute appendicitis at the local hospital, but anti-inflammatory and antispasmodic treatment did not appear to improve her symptoms. As the abdominal pain became more serious, the patient was admitted to our hospital for emergency treatment.

Physical examination revealed abdominal distention, slightly tight abdominal muscles, and a mass in the pelvic cavity. The mass, which was mobile and tender during palpation, was 4 cm from the top of the symphysis ossium pubis, with a transverse diameter of 10 cm. Results of abdominocentesis revealed faint yellow ascites fluid, and blood test results showed a leukocyte count of 18.28×109/L, absolute neutrophil count of 14.46×109/L, absolute monocyte count of 0.84×109/L, absolute basophil count of 0.33×109/L, and hemoglobin level of 94 g/L. Transrectal and abdominal ultrasonography revealed a 11.3×9 cm lobulated, hypoechoic, and solid mass in the pelvic cavity, with an inhomogeneous echo pattern. The mass was closely related with the adjacent intestinal canal, and sonolucent fluid was observed in the pelvic cavity. Color Doppler flow imaging revealed rich blood flow signals in the mass . Colonoscopy showed a small amount of dark red blood in the stool, a narrow lumen 10 cm from the anus, and smooth intestinal mucosa, which may have been due to external pressure .

The plain CT scan showed transmural growth of a dumbbell-shaped soft tissue mass (11.5×9×8 cm) with uneven density in six small intestine areas, and effusion was observed in the pelvic cavity (Figure1). The contrast-enhanced CT scan showed uneven arterial enhancement and delayed lesion enhancement, with the CT value reaching 149 HU (Figure 2-3). A patchy low-density non-enhanced area was observed in the mass, which had a clear boundary with the adjacent intestinal canal. The sigmoid colon was shifted due to compression. Blood was supplied to the mass through branches of the superior mesenteric artery. Soft tissue density nodules were observed in the mesentery, some of which showed central necrosis.

After the patient was admitted to our hospital, fresh blood was detected in the stool, and hemoglobin level was decreased to 71 g/L. Four days later, surgical resection of the tumor was performed under general anesthesia, which revealed that the tumor had an intact capsule and did not invade surrounding tissues. The tumor was located in the ileum 160 cm from the ileocecal valve. The corresponding mesostenium was cut, and the small intestine was cut 6 cm proximal to the tumor for complete resection. Gross examination of the specimen showed that the intestinal canal was 13 cm long with a 9-cm diameter. A dumbbell-shaped mass (10×8×6 cm) was observed 4 cm from one side of the incisal edge, with one end of the section (6×5.5 cm) protruding toward the mucosal surface, and the other end (6×4.5 cm) protruding toward the serosal surface. A grey and dark red mass (7×4.5×3 cm) was found near the two ends; the cut surface was grey and yellowish, and part of the mass was cystic and flexible. The postoperative pathology examination revealed numerous spindle cells arranged in dense bundles with diffuse infiltration of inflammatory cells, tumor involvement of the mucosa and serosa, and a negative margin. Immunohistochemistry results were ALK (+), α-SMA (-), h-caldesmon (-), S-100 (-), CD117 (-), DOG-1 (-), actin (-), and β-catenin (-). The diagnosis of IMT was based on immunohistochemistry and morphological characteristics (Figure4). Recurrence was not detected at the 3-month follow-up examination.

Discussion

IMT is a rare lesion originating from mesenchymal cells. Some cases have occurred after surgery, trauma, or inflammation; however, the pathogenesis remains unclear. The tumor was previously thought to be an abnormal response to tissue injury, involving uncontrolled proliferation of myofibroblasts. Given its low but documented risk of local recurrence and metastasis, IMT is currently regarded as a neoplasm with intermediate biological potential[3,4]. IMTs can give rise to sarcomas in some cases[5].

The histological features of IMT are variable. The tumor is composed primarily of myofibroblastic spindle cells and infiltrated by inflammatory cells such as plasma cells and lymphocytes. The proportion and growth of these cells varies among IMTs and even between different zones of the same IMT. Coffin et al. described three types of IMT: (1) mucus type consisting mainly of mucus, blood vessels, and inflammatory cells; (2) solid spindle cell type consisting mainly of spindle cells mixed with inflammatory cells; and (3) fiber type consisting mainly of dense and confluent collagen fibers. In this case, the pathology results showed spindle cells densely arranged in bundles and accompanied by diffuse infiltration of inflammatory cells (spindle cell type IMT)[6,7]. In conjunction with histomorphology, the role of ancillary studies in predicting the biological behavior of IMTs outside the female genital tract has been explored. Although p53 overexpression appears to be common in IMTs (up to 80% in one case series), its prognostic value is still uncertain[8].

Although IMTs can occur in any body part at any age, they are more common in female patients, especially children and adolescents. These tumors are frequently detected in the lung and rarely in parenchymal or hollow organs of the abdomen. Clinical manifestations include fever, fatigue, and weight loss, but clinical symptoms for IMTs in parenchymal organs are typically subtle and nonspecific. IMTs in hollow organs produce chronic abdominal pain and tenderness during physical examination. Most IMTs are benign and show a delayed course. These tumors have a tendency for local recurrence, but distant metastasis is rare. The few reported cases of tumor metastasis involved young females with acute symptoms accompanied by mesenteric metastasis. Treatment is typically surgical resection combined with chemotherapy[9,10]. Chromosomal rearrangements involving the anaplastic lymphoma kinase (ALK) gene have been observed in IMTs[11], suggesting the potential usefulness of ALK-targeted therapy for IMT.

Tumor uptake of fluorodeoxyglucose (FDG), a glucose analog used in medical imaging, is affected by cell components[12]. Combining FDG positron-emission tomography with CT may be useful for the detection of primary tumors, local recurrences, and distant metastases in patients with IMTs. However, FDG uptake is highly variable, possibly due to tumor cellularity, biological behavior of the tumor cells, composition of the inflammatory cell infiltrate, and the proportion and extent of activation of the inflammatory cells. Similarly, CT and magnetic resonance imaging characteristics of IMTs have been variable and nonspecific[13-15]. Abdominal IMTs are easily confused with other tumors or lesions, with typical imaging findings showing a mass with a clear border, obvious enhancement, and central necrosis. IMTs in the gastrointestinal tract may protrude into the abdominal cavity, appearing as round or garland-like structures. Early-phase contrast-enhanced CT shows either slight homogeneous enhancement or obvious enhancement, with a slow and continuous increase in contrast enhancement over time. The growth and imaging findings of the tumor in this case were similar to those of previous reports of IMTs.

Conclusion

CT imaging reveals the size and scope of the lesion, surrounding structures, relationship between the tumor and surrounding vessels, and tumor vessel morphology. Diagnosis is based primarily on tumor location and histopathologic appearance. In our patient, the lesion was detected in six areas of the small intestine, which distinguished it from gastrointestinal stromal tumors, fibrous histiocytomas, and lymphoma. Diagnosis of IMT was confirmed by histopathology and immunohistochemistry results.

Competing interests

The authors declare that they have no competing interests.

The author is grateful for the participation of the patient in this study and for assistance from colleagues in the general surgery Department of our Hospital.

References

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[pic]

Figure 1. Computed tomography imaging of the pelvic cavity shows transmural growth of a dumbbell-shaped soft tissue mass in six areas of the small intestine, with uneven density.

[pic]

Figure 2. Contrast-enhanced CT scan shows uneven arterial enhancement, delayed lesion enhancement, tumor blood supply from branches of the superior mesenteric artery, and obviously enhanced nodules with central necrosis in the mesentery.

[pic]

Figure 3: Coronal reconstruction showed that the delayed phase of the tumor was enhanced, and the lymph nodes along the distribution of the mesenteric lymph nodes

were clearly displayed.

[pic]

Figure 4. Numerous spindle cells are densely arranged in bundles with diffuse infiltration of inflammatory cells. Immunohistochemistry results confirmed the diagnosis of IMT.

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