Inflammatory myofibroblastic tumor (IMT) is a disease characterized by spindle cell neoplasm composed of lymphocytes, plasma cells, and so on. IMT is rare in clinical, which mainly located in the lungs. IMT has been defined by many different names, including inflammatory pseudotumor (IPT) and plasma cell granuloma, highlighting the complexity and variable histological characteristics of these tumors. Pettinato and colleagues in 1990 first put forward the concept of inflammatory myofibroblastic tumor (IMT) [2]. In the 2002, World Health Organization (WHO) classification of soft tissue tumors, these lesions were renamed [3].
The etiology of these ‘tumors’ is not certain and the current acquaintance of the pathophysiology of this disease is based on an abnormal response by the myofibroblast to trauma, tissue injury, surgery, inflammation and so on. Our patient admitted to hospital with a history of head injury in before two month age, which may be the inducing factors of this disease. Some cases have been associated with tuberculosis or malignancy as satellite lesions, and some suggested to be associated to cocaine consumption [4–6] and even by viral infection such as Epstein–Barr virus [4, 7]. There have been reported IMT in the spleen may be associated with EBV infection [8]. In addition, there are scholars believe that abnormal autoimmune mechanism may be related to the occurrence of a muscle fiber mother cell tumor. Plasma cell granuloma might be responsible for the immunological abnormalities because symptom of plasma cell granuloma was resolved as soon as the tumor was removed [9, 10]. Recent studies have confirmed that the chromosome 2p23 of IMT case is rearrangement, which hints the of the monoclonal hyperplasia characteristics of IMT and supports this lesion as true tumor rather than inflammatory pseudotumor [11, 12]. However, the lack of p53 detection in IMT gone with the low proliferation index (Ki67 < 10%) hints that IMT may be a low-grade tumor, if at all [13].
Making a diagnosis of IMT requires a histopathological examination because the radiological and clinical findings are generally nonspecific [1]. Research suggests electron microscopic observation is special. Under the electron microscope, this tumor cells are of ultra microstructure characteristics of fibroblast and myofibroblast cell, show the bipolar or irregular cellular processes, well-differentiated rough endoplasmic reticulum, and filament bundle of the surrounding cytoplasm, discontinuous base board structures and pinocytosis vesicles surrounding cells. Immunohistochemical can assist the diagnosis to this disease. Spindle cells of IMT is performance for different degrees of positive reaction to the following antibody: vimentin, SMA, MSA (muscle-specific actin). Positive reaction of vimentin is usually very strong, but its specificity is not high, because the vimentin can be found in all normal mesenchymal tissue and most sarcoma. Specificity of SMA is good, whose positive reaction is thought to be important marker to IMT. A small part of IMT is of positive reactions to epithelial membrane antigen, CK, CD68, CD30, α-antitrypsin, α-anticoagulant protease or melting bacteria enzymes, and so on, but no specificity to diagnosis [14]. This case was proved as IMT by immunohistochemical staining with Vim+, SMA+, actin+, desmin (partly cells +).
Steroids have been used to treat unresectable lesions and got some success. Other medical treatment choice, however, are less effective, including radiotherapy and/or adjuvant chemotherapy and treatment with immunosuppressive and anti-inflammatory drugs. Treated with high-dose corticosteroid anti-inflammatory drug, some patients symptoms can subside, but withdrawal symptoms once drug discontinuance. Methotrexate, azathioprine, vinca alkaloids, cyclophosphamide and cyclosporine have been used; however, the response is variable and often poor [15–18]. Fumiko et al. report a successful treatment case of an unresectable inflammatory myofibroblastic tumor of the frontal bone by methotrexate and cyclooxygenase-2 inhibitor [1]. In summary to the existing literature, there is a consensus that total surgical excision is the most effective therapeutic option in cases in which the tumors are surgically accessible.
Our patient received only surgical excision therapy. This patient got a good postoperative outcome with no recurrent signs according to follow-up MR imaging for about one year. However, it must be carefully observed especially for recurrent signs of the tumor.
