Asymptomatic inflammatory myofibroblastic tumor of the heart: immunohistochemical profile, differential diagnosis, and review of the literature.

Background: Inflammatory myofibroblastic tumor (IMT) is an uncommon lesion, mainly occurring in children and young adults and extremely rare in the heart. IMTs are composed of differentiated myofibroblastic cells accompanied by inflammatory cells. Cardiac IMTs are considered biologically benign, but they may have fatal consequences depending upon the peculiarity of site. Because of their rarity in the heart, most knowledge is based on extracardiac lesions that have uncertain behaviour.

Methods And Results: We investigated the morphologic features and the immunohistochemical profile of an intracardiac IMT, arising in the right outflow tract of an asymptomatic 11-month-old boy, by using a large panel of antibodies, many of them previously reported in extracardiac IMTs only. Results were compared with data of literature. After complete surgical excision of the tumor, the patient is disease-free at 1 year of follow-up.

Conclusions: The present case showed morphologic and immunohistochemical features characteristic of IMT. Immunohistochemistry was helpful for characterization and differential diagnosis. The immunoreactivity pattern (including calponin expression) was similar to that of extracardiac IMTs except for anaplastic lymphoma kinase 1 immunoreactivity, lacking in this benign intracardiac IMT but usually associated to favourable prognosis in extracardiac IMTs.