LETTER TO EDITOR
Year : 2010 | Volume
: 53 | Issue : 2 | Page : 382--384
Inflammatory myofibroblastic tumor of the infratemporal fossa
Raman Arora1, Alok Sharma1, Ruchika Gupta1, Bharati Malhotra2, Amit K Dinda1,
1 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Radiology, Dr. Baba Saheb Ambedkar Hospital, New Delhi, India
Amit K Dinda
Additional Professor, Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110029
|How to cite this article:|
Arora R, Sharma A, Gupta R, Malhotra B, Dinda AK. Inflammatory myofibroblastic tumor of the infratemporal fossa.Indian J Pathol Microbiol 2010;53:382-384
|How to cite this URL:|
Arora R, Sharma A, Gupta R, Malhotra B, Dinda AK. Inflammatory myofibroblastic tumor of the infratemporal fossa. Indian J Pathol Microbiol [serial online] 2010 [cited 2020 Aug 10 ];53:382-384
Available from: http://www.ijpmonline.org/text.asp?2010/53/2/382/64313
Inflammatory myofibroblastic tumors (IMTs) are rare myofibroblastic lesions and have been described in a variety of locations including lungs, mesentery, omentum, retroperitoneum and other sites. Inflammatory myofibroblastic tumor of infratemporal fossa has been only rarely reported in English literature. Recognition of this rare entity and distinction from soft tissue sarcomas is important in view of the unusual behavior and good response to complete surgical resection. 
We describe the case of a 37-year-old male presenting with a three year history of painful jaw opening accompanied by reduced mouth opening for the past one year and slight protrusion of left eyeball for the last six months. In addition, he noticed a gradually increasing fullness in the left temporal region. Local examination revealed a diffuse firm fullness in the left temporal area. There was trismus and axial proptosis on the left side. Contrast enhanced computed tomography (CECT) scan revealed a homogenous mildly enhancing soft tissue density in the left temporal and infratemporal regions with lytic destruction of the left ramus of mandible and extending close to the skull base till the pterygoid plates [Figure 1]. A biopsy from the mass showed fibrocollagenous tissue with few inflammatory cells, and was interpreted as inconclusive. With a clinical suspicion of soft tissue sarcoma of left temporal region, the patient underwent an excision of the mass. A complete excision of the mass was not possible due to indistinct surgical margins of the lesion.
The resected specimen consisted of multiple pieces of gray-white soft tissue along with pieces of bone. Multiple sections showed a tumor composed of fascicles of spindle cells arranged in an interlacing network with a focal storiform arrangement. These cells had oval to elongated nuclei showing mild pleomorphism. No significant nuclear atypia was noted. Mitotic figures were frequent (3-5 per 10 high power fields), though no abnormal mitosis was seen. In addition, a prominent inflammatory component composed of mature lymphocytes and plasma cells was noted [Figure 2] a-c. Immunohistochemistry revealed the spindle cells to be positive for vimentin and focally for smooth muscle actin (SMA) and were negative for cytokeratin, desmin, CD34 [Figure 2]d and S-100 protein. A final pathologic diagnosis of inflammatory myofibroblastic tumor of the left temporal and infratemporal region was rendered.
Postoperatively, there was an improvement in mouth opening along with significant reduction in proptosis. A repeat CECT scan, four months after surgery revealed a residual mass in the left temporal region extending to the left cavernous sinus. The patient was initiated on corticosteroid therapy and is currently on close clinical follow-up.
Inflammatory myofibroblastic tumor is a lesion composed of myofibroblastic spindle cells accompanied by variable numbers of plasma cells and/or lymphocytes.  Inflammatory myofibroblastic tumor has been reported at various locations including lung, pleura and abdominal organs.  In head and neck region, IMT usually involves the orbit and is rarely seen in maxillary sinus, pterygopalatine fossa, nasopharynx and skull base. ,, We report a rare case of IMT in the infratemporal fossa with extension into the temporal fossa and local destructive effects, simulating a malignant process. Other clinical differential diagnoses to be considered in such a case include temporomandibular joint dysfunction and various sarcomas, especially in view of the radiological appearance of an infiltrative lesion. Inflammatory myofibroblastic tumor involving infratemporal fossa has been earlier reported in orbital IMT with intracranial extension. 
The clinical and radiological appearances of IMT especially with the presence of infiltrative soft tissue mass with destruction of adjacent bones, raises a suspicion of malignant neoplasm, which would require a radical surgery.  Hence, histopathological evaluation remains the mainstay of diagnosis of IMT.
Histological examination of IMT demonstrates myofibroblastic spindle cells in a variably prominent collagenous stroma along with an inflammatory component of lymphocytes and plasma cells. Mitotic figures are variable and may be quite frequent but not atypical.  The differential diagnosis of IMT includes both benign and malignant tumors. Sclerotic forms of IMT may be mistaken for aggressive fibromatosis. The cellular variants of IMT may be confused with other spindle cell malignant neoplasms like leiomyosarcoma or fibrosarcoma. Leiomyosarcoma usually displays a more regular fascicular pattern, cigar-shaped nuclei and an absence of inflammatory infiltrate. Inflammatory fibrosarcoma is an entity, which may be related to IMT since they share clinical and pathologic features, including pronounced cytological atypia.  In our patient, the final diagnosis of IMT was rendered considering the low grade nuclear features, prominent inflammatory component and the immunohistochemical evidence of myofibroblastic differentiation of the tumor cells (positivity for vimentin and smooth muscle actin).
Surgical excision is the mainstay of therapy, including recurrent tumors. The role of chemotherapy and radiotherapy remains to be established. 
In conclusion, inflammatory myofibroblastic tumor is an uncommon soft tissue neoplasm, occurring rarely in the infratemporal fossa. It may be misdiagnosed as a soft tissue sarcoma on a clinico-radiologic examination due to the locally destructive nature of the tumor. An accurate histopathological diagnosis is essential for appropriate surgical therapy and requires attention towards demonstration of myofibroblastic nature of the constituent tumor cells using ancillary techniques.
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