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

Abstract

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<0.001). As an exclusion criterion of IgG4-related IPT, ALK-positivity was correlated with the higher cytological atypia (mean 3.7/HPF, P<0.001) and lesser lymphoid follicles (mean 1.2/HPF, P=0.021). And it's the first study to show the liner positive correlation between the lymphocytes + plasma cells count and IgG4-positive plasma cells count in these lesions (r=0.914, P<0.001). The negative correlation between the IgG4-positive plasma cells count and the expression of ALK-1 are reported for the first time as well (rs=−0.632, P=0.001). However, despite two patients with recurrence or metastasis were divided into IMT group, only borderline values were detected in the survival analysis (OS 88.89% 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.

The Clinical and Radiological Characteristics of Inflammatory Myofibroblastic Tumor Occurring at Unusual Sites

“…It can occur anywhere in the body but is most frequently documented in the lung, retroperitoneum, and gastrointestinal tract [3], and it is rarely located in the soft tissue of the extremities, bones, or joints. A proportion of IMT cases exhibit local recurrences and occasional distant metastases which cannot be well explained by an inflammatory reaction [4]. …”

Transbronchial lung biopsy for the diagnosis of IgG4‐related lung disease

“…The present results suggest that IgG4‐positive plasma cell infiltration in TBLBs has 98% specificity for the diagnosis of IgG4‐RD. Previous studies investigated the number of IgG4‐positive plasma cells and/or the IgG4/IgG‐positive plasma cell ratio in biopsy specimens of various inflammatory diseases . Increased numbers of IgG4‐positive plasma cells or elevated IgG4/IgG‐positive plasma cell ratios were observed not only in IgG4‐RD, but also in other inflammatory conditions, including obstructive sialadenitis, oral inflammatory lesions, inflammatory bowel diseases, diverticulitis, rheumatoid or non‐specific synovitis, plasma cell‐rich dermatitis, and carcinomas with an inflammatory response rich in plasma cells .…”

Pulmonary inflammatory myofibroblastic tumour and IgG4-related disease presenting with lower limb paralysis

“…IMT is composed of differentiated myofibroblastic spindle cells with excessive inflammatory cell infiltration, differentiating it from IgG 4 -RD. Detection of anaplastic lymphoma kinase expression is helpful in the differential diagnosis of IMT and IgG 4 -related inflammatory pseudotumours 2. Some IMTs are functional tumours, associated with paraneoplastic syndromes 3.…”