Metastatic inflammatory myofibroblastic tumor identified by EUS-FNA in mediastinal lymph nodes with ancillary FISH studies for ALK rearrangement.

Inflammatory myofibroblastic tumor (IMT) is an exquisitely rare neoplasm with a low incidence of metastasis. Previously, cytologic diagnosis of this entity, by fine needle aspiration (FNA) or endoscopic ultrasound guided fine needle aspiration (EUS-FNA), was challenging, if not impossible. However, advancements in the field of molecular pathology, the applications of which have lagged in cytopathology relative to other disciplines, now makes diagnosis possible. Here we report a case of pulmonary inflammatory myofibroblastic tumor with mediastinal nodal metastasis in a 74-year-old man, definitively diagnosed by EUS-FNA utilizing morphologic, immunohistochemical, and molecular findings, including fluorescent in situ hybridization studies for ALK gene rearrangement. This case report demonstrates the value of ancillary molecular studies to assist in the diagnosis of rare neoplasms, including those at sites of metastasis.