Head and neck inflammatory myofibroblastic tumor (IMT): evaluation of clinicopathologic and prognostic features

Abstract

Owing to rarity and awareness deficiency towards inflammatory myofibroblastic tumor (IMT), we sought to review on its clinicopathological features; arising awareness to achieve early diagnosis; exploring prognostic factors and then establishing a treatment protocol. Retrospective study was performed on patients with histological proven IMT between January 2003 and December 2010. Their demographic data, clinical and histological presentations were recorded. Overall survival (OS) and progression-free-survival (PFS) were estimated via Kaplan-Meier method. Cox regression model was applied to determine the significant of prognostic factors. Logistic regression model was established to predict the probability of relapse. A total of 28 patients. Five-year PFS was 65%. Surgical margins primarily and independently determined the survival, followed by size, pseudocapsule of the lesion, intra-lesional necrosis and lastly Ki-67 and ALK overexpression. Logistic model in prediction of relapse was established, with the formula as probability of relapse = 1/(1 + e(-z)) where e = exponential function, z = constant value (3.9) + B*margin + B*size + B*immunohistochemical expression + B*pseudocapsule + B*intra-lesional necrosis. Immunohistochemical overexpression was significant if Ki-67 was strongly expressed with a conditioned ALK overexpression simultaneously. Staining intensity must be at least moderate for those ALK nuclear staining was less than 25%. Weak ALK staining intensity is only significant if nuclear staining was more than 25%. Diagnosis of IMT is achieved via exclusion. Radical resection and obtaining negative margins remains the mainstay of treatment. Both high and moderate-risk groups required post-operative radiotherapy. In low-risk group, post-operative radiotherapy was recommended if the lesion is larger than 5 cm in diameter with a conditioned ALK & Ki-67 overexpression.