Inflammatory myofibroblastic tumor of the oral cavity: review of the literature and presentation of an ALK-positive case

Abstract

Inflammatory myofibroblastic tumor (IMT) is a controversial lesion composed of myofibroblastic spindle cells accompanied by varying numbers of inflammatory cells. Although various pathogenetic (ie, reactive, infectious, autoimmune, and neoplastic) factors have been implicated, the etiology of most IMTs remains unknown. Here, we present a case of IMT arising from the mandibular alveolar mucosa of an 82-year-old female. The lesion presented as a 5 × 5 cm round pedunculated painless mass of 2 months' duration, associated with a superficial resorptive defect of the mandible. The lesion was surgically removed and, on histopathologic examination, appeared to be composed of plump spindle cells set in a myxoid vascular stroma admixed with an inflammatory component consisting primarily of neutrophils and lymphocytes. Numerous large “ganglion cell–like” cells were dispersed throughout the lesion. Only occasional mitotic figures were encountered, in the absence of cytologic atypia. Ultrastucturally, prominent myofibroblastic features were seen. Immunohistochemical analysis revealed that the spindle and ganglion-like cells were diffusely positive for vimentin, smooth muscle actin, and anaplastic lymphoma kinase (ALK), focally positive for CD68, and negative for desmin, bcl-2 and EBV-LMP. No evidence of recurrence has been noted at a 12-month follow-up. Including our patient, only 14 cases of oral IMT have been described in the literature. Patients' age ranged from 2 to 82 years with a mean of 35 years, and a 1.6:1 female predilection was noted. The buccal mucosa was the most commonly affected site (50%), followed by the mandible (21%). None of the reported cases of oral IMT recurred or metastasized. The present case is the second reported ALK-positive oral IMT, which points to a potential neoplastic origin. Significant differences in the clinical behavior and immunohistochemical and genetic profile of lesions diagnosed as IMT may indicate that the term has been used to describe lesions with similar histology but variable etiopathogenesis and prognosis.