Pulmonary inflammatory myofibroblastic tumor versus IgG4-related inflammatory pseudotumor: differential diagnosis based on a case series

摘要

Background: Pulmonary inflammatory myofibroblastic tumor (IMT) has been considered as a synonym for inflammatory pseudotumor (IPT) for a long time. Recent studies have indicated that IMT and IgG4-related IPT are distinct diseases. However, no consensus criteria have been recommended. Here we propose a set of criteria for the differential diagnosis. Methods: Twenty-six archived IMT and IgG4-related IPT samples were examined for histological characteristics and the expression of IgG, IgG4, SMA and ALK-1. Based on our proposed criteria, we reclassified the cases into either IMT or IgG4-related IPT group and compared the clinicopathological features, laboratory findings, overall survivals (OS) and disease-free survivals between groups to validate the effectiveness and dependability of the diagnostic criteria. Results: The average age of IgG4-related IPT group was higher than IMTs (48.82 vs . 39.22 years, P=0.031). In IMT group, tumors were characterized by bigger tumor sizes (3.47 vs . 2.22 cm, P=0.007), diffuse and total destroyed alveoli (88.89% vs . 17.65%, P=0.002), fewer lymphoid follicles (1.6/HPF vs . 3.0/HPF, P=0.045) and lower expression of IgG (74.7/HPF vs . 149.1/HPF; P vs . 100%, P=0.197, DFS 77.78% vs . 100.00%; P=0.056). Conclusions: The significant differences of clinicopathological characteristics between the IMTs and IgG4-related IPTs indicated that a combination of lymphocytes + plasma cells count, cytological atypia, IgG4 and ALK-1 staining will be helpful in differential diagnosis.