Inflammatory myofibroblastic tumor of the lung in children: anaplastic lymphoma kinase (ALK) expression and clinico-pathological correlation.

The inflammatory myofibroblastic tumor (IMT) is a rare neoplastic lesion with a high incidence in children and young people, and may arise in lungs, soft tissue, or viscera. It is recognized as a borderline tumor with the possibility to recur, undergo malignant transformation, and metastasize. IMT is composed of fascicles of bland myofibroblastic cells admixed with an inflammatory infiltrate consisting of lymphocytes, plasma cells, and eosinophils. We reviewed pulmonary IMT diagnosed at Garrahan Hospital in Buenos Aires, Argentina, during 12 years and examined the clinical, laboratory, and pathological features as well as molecular genetics. Eight pediatric cases were evaluated with a male-to-female ratio of 5:3 and a median age of 6 years at diagnosis. The most common lung localization was the upper lobe. All cases underwent surgical excision and no local recurrences were found. Five out of eight patients, including two cases with metastatic/multifocal lesions in the central nervous system (CNS), are alive and disease free after a median follow-up of 30 months. Anaplastic lymphoma kinase (ALK) expression was negative in all pulmonary samples by immunohistochemistry (IHC), however, rearrangement for ALK locus by fluorescence in situ hybridization was found in one lung and in two CNS samples. These findings may reflect higher sensitivity of the molecular biologic procedure compare to traditional IHC practice. In our pediatric experience, 25% of patients with lung IMT developed CNS lesions; therefore we consider that CNS screening in these patients should be considered, at diagnosis and later during follow up.