Involvement of 2p23 in pulmonary inflammatory pseudotumors

Pulmonary inflammatory pseudotumors (IP) are rare mesenchymal proliferations that have a polymorphic histology and an unpredictable biologic behavior. The histologic spectrum of TP has led to uncertainty as to whether this tumor has a reactive or neoplastic pathogenesis, Reports of extrapulmonary IP have identified clonal chromosomal aberrations involving 2p23 in the region of the ALK gene. Using fluorescence in situ hybridization with a probe flanking the ALK gene at 2p23 and immunostaining for the ALK gene product, we studied formalin-fixed, paraffin-embedded tissues of pulmonary IP and found a subset (33%) with 2p23 aberrations. We suggest that chromosomal rearrangements and ALK immunostaining may be helpful in the diagnosis of a group of pulmonary IP and should be investigated as a potential tool for predicting their future biologic behavior. An association with anaplastic large-cell lymphoma was also observed.