[1661] Do Inflammatory Myofibroblastic Tumors (IMT) and IgG4 Related Lymphoplasmacytic Sclerosing Lesions (IgG4-RLSL) Have a Similar Pathogenesis?

Shahid J Bokhari, Jan F Silverman, Alok Mohanty. Allegheny General Hospital, Pittsburgh, PA

Background: IgG4-RLSLs is most frequently described in the pancreas and salivary gland, but have also been recently reported with increasing frequency in a variety of body sites. Diagnostic histologic features of IgG4-RLSL include infiltration of plasma cells that express IgG4, areas of dense sclerosis and phlebitis. Some of these morphologic features are also shared by IMTs, including the presence of numerous plasma cells and fibrosis. While IgG4 plays a central role in IgG4-RLSLs, there is scant literature evaluating the role of IgG4 in IMT. We studied the presence of IgG4 positive plasma cells in IMT to determine if it possibly shares a possible common pathogenesis with IgG4-RLSL.
Design: A total of 16 cases of IMTs with H&E slides and corresponding tissue blocks were retrieved from the hospital computer system. All selected cases had been previously confirmed as IMTs by histology and immunohistochemistry (IHC) panel that included smooth-muscle actin and anaplastic-lymphoma kinase (ALK). In addition, IHC for IgG4 was also performed on tissue-block sections that were formalin-fixed and paraffin embedded, using a heat-induced epitope retrieval technique.
Results: 16 IMTs were included in our study from the following sites: 5/16 from the orbit, 3/16 from the lung, 2/16 from the kidney, and one each from the liver, breast, colon, bladder, small intestine, and lymph node. 15/16 (93.8%) IMTs demonstrated IgG4 positive plasma cells. Of these 15 cases, 11/15 (73.3%) showed at least 90% of all plasma cells being positive for IgG4, 2/15 (13.3%) showed at least 50% of all plasma cells being positive for IgG4, and 2/15 (13.3%) showed at least 20% of all plasma cells being positive for IgG4. All cases showing at least 90% of plasma cell positivity for IgG4 demonstrated both strong membranous and cytoplasmic staining. 7/15 (46.7%) were ALK negative, and 8/15 (53.3%) were ALK positive. Pattern and intensity of staining was identical in the ALK negative and ALK positive cases. A single IMT in our study was negative for IgG4 and ALK.
Conclusions: Our results indicate that IMTs contain a significant number of IgG4 positive plasma cells. These findings raise the possibility that IMTs and IgG4-RLSLs not only can show similar morphologic features characterized by inflammation and sclerosis, but may also share a common pathogenesis.
Category: Pathobiology

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 236, Wednesday Morning

 

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