Inflammatory myofibroblastic tumor (IMT) is a rare tumor;[1] its clinical presentation and auxiliary examinations lack clinical specificity, often leading to misdiagnosis. IMT originates in many parts of the body, but occurrence in the greater omentum is uncommon. Anaplastic lymphoma kinase (ALK)-positive IMT with a diameter greater than 8 cm is extremely rare. Here, we present a case with a literature review to improve the IMT diagnostic rate.
CASE REPORT
Medical history
A 4-year-old female was referred to our hospital with a 1-month history of intermittent fever. She had a recurrent fever without inducement three to four times a day; temperatures ranged from 36.2°C to 39.2°C. No improvement was observed after 10 days of anti-inflammatory treatment. Physical examination revealed a left upper quadrant abdominal mass with unclear and tough margins.
Laboratory examination
Pre-operation: RBC 2.90 × 1012/L, HGB 67 g/L, PLT 738 × 109/L, CRP 137.90 mg/L, PCT 0.28 ng/mL, IL-6 256.20 pg/mL. No abnormalities were detected in human chorionic gonadotropin, alpha-fetoprotein, neuron-specific enolase, lactate dehydrogenase, 24-h urine catecholamine test, and blood aerobic culture. Sternal bone marrow puncture suggested proliferative anemia.
Image examination
Ultrasonography revealed a unilateral 6.2 × 4.9 × 6.2-cm lump in the left adrenal gland; the contralateral gland was normal. Computed tomography (CT) revealed a 6.4 × 5.5 × 6.5-cm lesion between the spleen and stomach. Enhanced CT detected an unclear boundary between the spleen and pancreatic tail, more closely related to the spleen [Figure 1]. Additional movie files 1 and 2 show this in more detail. Positron Emission tomography-CT revealed no systemic bone metastases.
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Figure 1: CT images before the operation. (a) plain CT scan; (b-d) contrast-enhancement CT scan (a and b) axial plane; (c) coronal plane; (d) sagittal plane. Axial, coronal, and sagittal computed tomography (CT) scans with contrast show a large mass between the stomach and spleen
Therapy and pathology
Concentrated red blood cells and plasma were given to correct anemia, and meropenem was administered as an anti-inflammatory treatment, but no obvious effects were observed. The mass was diagnosed as IMT by pathological tissue collected via ultrasound-guided puncture.
We considered that the fever was caused by IMT, excluding the factor of infection. With the presumptive diagnosis of IMT arising from the abdomen, we confirmed that the mass originated in the greater omentum during the operation. The mass was completely resected, and a negative margin was achieved. The maximum cross-sectional area of the tumor after surgery was 8.3 × 7.5 cm [Figure 2]. The largest cross-sectional area in the postoperative pathology report was 8 × 7 cm. The final pathology was consistent with the puncturing pathology. During the 8 months of follow-up, no local recurrence or metastasis has been observed [Figure 3]. Additional movie files 3 and 4 show this in more detail.
Figure 2: Images during the operation and images of the tumor. (a) This image shows that the tumor is attached to the spleen, but not from the spleen (b-d) The maximum cross-sectional area of the tumor is 8.3 × 7.5 cm; the tumor is irregular in shape and tough in texture
Figure 3: CT images after the operation. (a and b) axial plane (a) plain CT scan; (b) contrast-enhancement CT scan. Axial computed tomography (CT) scan with contrast 5 months after the operation shows no recurrence of the tumor at the original site
DISCUSSION
IMT is a rare tumor[1] first found in the lung[2] and has since been observed in the mesentery, omentum, gastrointestinal tract, urogenital tract, upper respiratory tract, and soft tissue.[3] Among these tumor sites, IMT in the greater omentum is extremely rare. IMT was defined by the World Health Organization (WHO) in 2002 and classified as an intermediate tumor in 2006.[4] In 2013, the WHO defined IMT as “consisting of differentiated myofibroblast and fibroblast, accompanied by plasma cells, lymphocytes, eosinophils, and other inflammatory cells,” and a few parts of IMT were classified as transferable tumors.[5]
IMT of abdominal parenchymal or empty viscera are typically smaller (diameter <5 cm), whereas retroperitoneal lesions are larger (diameter >5 cm). However, in this case, an IMT originating in the greater omentum was greater than 8 cm in diameter, suggesting that IMT is clinically variable and has no specific manifestations. Therefore, we reported this extremely rare clinical case.
IMT most commonly occurs in children,[1] and the clinical presentation depends on the tumor site.[6] Abdomen-originating IMT is characterized by abdominal mass with fever, growth retardation, loss of weight, anemia, thrombocythemia, erythrocyte sedimentation rate (ESR), and immunoglobulin elevation.[7] Some metrics (fever, growth, weight, anemia, and thrombocythemia) are consistent with our report.
No specific laboratory test results confirm the disease,[1] but interleukin-6 showed the greatest pre- to postoperative change (RBC 4.37 × 1012/L, HGB 119 g/L, PLT 512 × 109/L, CRP 38.20 mg/L, PCT 0.62 ng/mL, IL-6 21.48 pg/mL), suggesting that fever was related to interleukin-6.
Pathology is the gold standard for diagnosing IMT[8] and is mainly based on the following indicators: ALK (+), Vim (+), SMA (+), S100 (−), and spindle cells. ALK is related to IMT, and the sensitivity of ALK in children is higher than that in adults, which can be used as a diagnostic auxiliary indicator.[9] Thus, multidisciplinary investigation before surgery is necessary.[10]
Complete surgical resection with a negative margin is an independent risk factor affecting prognosis.[11] Cases with negative surgical margins had an 87% reduction in death as compared to those with macroscopic positive surgical margins.[12] Preoperative pathological diagnosis can prevent the expansion of surgical scope and excessive treatment. Small hidden lesions should be explored and resected during surgery to reduce the risk of recurrence. When the tumor closely adheres to the surrounding tissues and organs, and the boundary is not obvious, comprehensive treatment, including chemotherapy, anti-inflammatory, and ALK inhibitors (crizotinib[13]) should be combined. IMT treatment with ALK inhibitors is a recent research direction. Cyclooxygenase-2 inhibitors, which act via the down-regulation of vascular endothelial growth factor expression, direct inhibition of endothelial cell proliferation and activation, and anti-cytokine,[1415] are used to reduce the size of larger IMTs, enabling surgical resection. If both ALK and Ki-67 are positive, postoperative treatment should include radiotherapy and chemotherapy.[12]
IMT prognosis is dictated by the tumor size and location, complete resection, and adjuvant therapy. The recurrence rate of IMT ranges from 18% to 40%. The recurrence rate is 35% with multiple-organ involvement and 6% with single-organ involvement.[16] The relationship between Ki-67, pathological type, ALK, and prognosis remains controversial, and larger samples are needed to analyze the correlation between these factors and prognosis. With every 1 cm increase in diameter, the risk of IMT relapse increases by 60%.[12] Diameters greater than 8 cm are significantly associated with aggressive behavior.[17] So, for children with ALK- and Ki-67-positive IMT of the greater omentum with a diameter greater than 8 cm, close attention should be paid to follow-up.
We report a case in which IMT occurred in the greater omentum with ALK-positive and a diameter > 8 cm. However, because of its clinical manifestations, laboratory tests and imaging have no obvious specificity, and the diagnosis of IMT mainly depends on pathology. Therefore, an accurate pathological diagnosis has to be obtained before surgery, and a negative margin has to be ensured during surgery. Close follow-up and collection of relevant cases should be conducted to explore prognostic factors.
Ethics approval and consent to participate
The present study was approved by the Medical Ethics Committee of Shandong Provincial Hospital.
Financial support and sponsorship
This work was supported by the grants from the Science and Technology Development Plan Project of Shandong Province, China (2014GSF118144, 2018GSF118209, 2019GSF108061), the Jinan Science and Technology Bureau (202019134), and the Shandong Provincial Natural Science Foundation (ZR2017MH091, ZR2020QH263).
Conflicts of interest
There are no conflicts of interest.
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