International Journal of Pediatric Otorhinolaryngology Extra 6 (2011) 272–274

Case report

Inflammatory myofibroblastic tumor of the tetromolar trigon§

Mehmet Yilmaz *, Erkan Kilic, Yusuf Haciyev, Ozcan Ozturk, Murat Toprak

Istanbul University, Cerrahpasa Medical School, Department of Otorhinolaryngology, Istanbul, Turkey

A R T I C L E I N F O

Article history:

Received 18 October 2010

Received in revised form 4 January 2011

Accepted 8 January 2011

Available online 2 February 2011

Keywords:

Inflammatory myofibroblastic tumor

Retromolar trigon

A B S T R A C T

Inflammatory myofibroblastic tumor (IMT) of the oral cavity is an extremely rare clinical and

pathological disease entity. It was originally described in the lung but has recently been reported in a

variety of locations including lungs, mesentery, omentum, retroperitoneum and other sites. IMT is an

unusual tumor composed of differentiated myofibroblastic spindle cells usually accompanied by

numerous plasma cells and lymphocytes. We report such a case of inflammatory myofibroblastic tumor

of the retromolar trigon in a 11-year-old girl. The patient presented with a soft tissue mass in the

retromolar trigon. Histologically, the lesion is dominated by differentiated spindle cells with aprominent

collagenous stroma and an inflammatory component including plasma cells and lymphocytes, and with

positive immunoreactivity for smooth muscle actin (SMA) and vimentin. The absence of cytologic atypia

helps differentiate this lesion from malignant spindle cell tumors.

� 2011 Published by Elsevier Ireland Ltd.

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International Journal of Pediatric OtorhinolaryngologyExtra

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1. Introduction

Inflammatory myofibroblastic tumor (IMT) is a rare soft-tissuetumor. These tumors have a pathologic differentiation of dominantspindle cell proliferation with a variable inflammatory component.These lesions are diagnosed as masses relating to their anatomiclocation [1]. Histologically, it is a benign entity, although clinicallyit is invasive. IMT is usually cured by surgical resection. It wasinitially described by Pettinato et al. [2] in 1990 in 20 lesions of thelung. Subsequently, it has been recognized that analogous tumorscan occur in various sites other than the lung, including theabdomen, skin and soft tissue, head and neck, gastrointestinaltract, and mediastinum with a higher prevalence in children andyoung adults [3–6].

The aetiology and the pathogenesis of IMT are still uncertainand difficult to be determined, even whether the disease is eitheran inflammatory reactive lesion or a neoplastic process. Pre-existing bacterial, viral and fungal infections, have been proposedas contributing factors [7–9]. On the other hand, trauma, surgery,steroids [10], previous radiotherapy and chemotherapy [7,8,11],allogenic hemopoietic stem cell transplantation [12], unrelatedumbilical cord blood transplantation [13] and renal allograft [14],have been suggested as possible aetiological co-factors.

§ This material has never been published and is not currently under evaluation in

any other peer-reviewed publication.

* Corresponding author at: Otolaryngology Department, Cerrahpasa Medical

Faculty, Istanbul University, Istanbul, Turkey. Tel.: +90 505 234 9813.

E-mail address: drmofly@yahoo.com (M. Yilmaz).

1871-4048/$ – see front matter � 2011 Published by Elsevier Ireland Ltd.

doi:10.1016/j.pedex.2011.01.001

2. Case report

A 11-year-old girl presented with a soft tissue mass of fourmonths duration in the retromolar trigon. On presentation, shecomplained lack of appetite without weight loss. There were noabnormal hematological examination, and biochemical analyses ofblood were within normal range. Oral examination revealed anoval-shaped tumor (3 cm � 2 cm) of the left posterior mandibleextending from the left retromolar trigon to that of the anteriorplica of palatine tonsilla, which was covered with pinkish-redmucosa (Fig. 1). On palpation, the tumor had a firm, elasticconsistency, irregular margins, and a smooth surface. The marginof mass lesion was noted on the computed tomography (CT) scan(Fig. 2). The tumor mass was easily excised totally by transoralapproach. The final pathology report gave the diagnosis of IMTwithout extending to the margins of the surgical specimen.Microscopic examination showed spindle tumor cells arranged inan irregular pattern with variable cell density. The tumor wasinfiltrated by some plasma cells, lymphocytes, and few neutrophilgranulocytes. The spindle cells showed mild atypia, and no mitoseswere observed (Fig. 3). Immunohistochemically, the tumor showedpositive immunoreactivity for vimentin and a-smooth muscleactin but not for either desmin or caldesmon (Fig. 4). However, thewound healed without problems. The postoperative course wasuneventful, and she was followed for 18 months, withoutrecurrence being observed.

3. Discussion

Inflammatory myofibroblastic tumors are mesenchymal solidtumors preferentially occurring in children and young adults. They

Fig. 1. Intraoral view showing an obviously firm, exophytic pink mass covered with

smooth mucosa, measuring 30 mm � 20 mm, localized in the retromolar trigon

mucosa (margins were determined with white arrows).

Fig. 3. Microscopically, the fascicular area is composed of eosinophilic spindle cells

with numerous inflammatory cells including lymphocytes, plasma cells, and few

granulocytes [hematoxylin–eosin (HE), original magnification, 400�].

M. Yilmaz et al. / International Journal of Pediatric Otorhinolaryngology Extra 6 (2011) 272–274 273

present as proliferating myofibroblastic cells together withplasmocytes and lymphocytes. The most common site of involve-ment is the lung. Other less common sites include the gastrointes-tinal tract, genitourinary system, and upper aerodigestive tract [1].These tumors are rarely encountered in the head and neck. Theorbit, larynx, oropharynx, and paranasal sinuses are more ofteninvolved. Whereas extrapulmonary tumors tend to occur inchildren, tumors in the head and neck occur more often in youngadults [1].

The aetiology of these lesions is unknown, with various reportsindicating infection or an abnormal immunological reaction aspossibilities. Recent cytogenetic and molecular observations haveshown abnormalities in chromosomal band 2p23, resulting in arearrangement of the ALK gene. This finding of a specific genetic

Fig. 2. The margin of mass lesion was noted coronal and axial plan on the computed tom

and black arrows in axial section).

alteration suggests a more neoplastic aetiology than a reactiveinflammatory process [8,15].

IMT is histopathologically composed of myofibroblastic spindlecells, with an inflammatory cell infiltrate of plasma cells,lymphocytes and eosinophils, and different patterns can be foundwithin the same tumor [16]. Immunohistochemistry is a valuableadjunct to light microscopic diagnosis. Vimentin is almostinvariably positive in the spindle cells. Smooth muscle actin,muscle-specific actin and desmin are present in majority of thecases. CD68 (KP-1), CD30 (Ki-1), cytokeratin and p53 are positive insome cases [3].

IMTs have a variable biologic behavior that ranges from thefrequently benign lesions to more aggressive variants. Predictive ofaggressive behavior is cellular atypia; ganglion-like cells; necrosis;nucleolar prominence; and mitotic activity, including atypicalmitotic figures expression of p53 and anueploidy [16]. Anextrapulmonary location of the tumor is more frequent inchildhood. Coffin et al. [3] reported 84 patients with extra-pulmonary IMT, who were all children and adolescents. Adult casesare even rare in this study. Of the 53 patients under follow-up, 13(25%) had one or more recurrences at 1–24 months after initial

ography (CT) scan (margins were determined with white arrows in coronal section

Fig. 4. Immunohistochemically, the tumor cells show diffuse and intense

immunoreactivity for SMA (original magnification, 400�).

M. Yilmaz et al. / International Journal of Pediatric Otorhinolaryngology Extra 6 (2011) 272–274274

excision, and distant metastases were not documented. Accordingto them, an inflammatory myofibroblastic tumor is a benign,nonmetastasizing proliferation of myofibroblasts with a potentialfor recurrence and persistent local growth, similar in some respectsto fibromatosis. Spontaneous regression has also been reported insome cases of IMT [17]. In general, the primary therapeuticapproach is surgery for complete resection if the anatomic locationis amenable. Inadequate resection has been shown to be a riskfactor for recurrence. For incomplete resection, adjuvantapproaches using corticosteroids, COX-II inhibitors or chemother-apy and radiation have been attempted with limited success [3].

4. Conclusion

IMT is a very unusual benign pathology in the oral andmaxillofacial area. Because of its aggressive clinical and radiologicfeatures, we may mistake it as a malignancy, and therefore thoroughpathological investigation is mandatory. The diagnosis and progno-sis are highly dependent on complete surgical resection.

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