Inflammatory fibroid polyp: A series of 29 cases and a systematic review of the literature

• Published in: Human Pathology Reports 2023-06, Vol.32, p.300703, Article 300703
• Main Authors: Maccagno, Andrea, Sander, Björn, Dintner, Sebastian, Harloff, Manuela, Füzesi, László, Märkl, Bruno
• Format: Article
• Language: English
• Subjects: IgG4-Pseudotumor; Inflammatory fibroid polyp; Inflammatory tumor, PDGFRA; Vanek tumor
• ISSN: 2772-736X; 2772-736X
• DOI: 10.1016/j.hpr.2023.300703

•A patient consent statement was not necessary for this manuscript.•Use of the tissues was approved by the local ethics committee in Munich (Reference number 21-1191).•All analyses were performed on old paraffin blocks and had no influences on the diagnosis and treatment of patients. An inflammatory fibroid polyp (IFP) of the gastrointestinal tract is a localized, benign mesenchymal lesion consisting of spindle-shaped stromal cells, eosinophilic granulocytes, and some lymphocytes and plasma cells. The discovery of a frequent mutation of the platelet-derived growth factor receptor A (PDGFRA) gene was the first hint of a gene-regulating process in IFPs. The aim of this study was to investigate the interaction of inflammatory processes and the role of mutation and expression of the PDGFRA gene in the development of IFPs for the first time. We used immunohistochemistry to analyze the composition of inflammatory cells and next generation sequencing (NGS) to provide a broad overview of gene mutations. We report on 29 cases of IFP. The mean age, gender differences, and localization were compatible with the literature. Spindle cell histomorphology was present in 79% of cases showing a typical onion skin-like perivascular arrangement and significantly high CD34 positivity (p = 0.002, Fisher’s exact test). Eosinophilic granulocytes were present in an average density of 60 ± 49/high power field (HPF) (range: 15–200), and there was a significantly higher rate of IFPs larger than 2 cm in size (p = 0.018, Wilcoxon test). All but one cases could be analyzed by NGS. Mutations were observed in 17 cases (60.7%), including 13 (46.4%) mutations in the PDGFRA gene. Among the gastric lesions, mutations were found in exon 18 of the PDGFRA gene with amino acid exchange (Asp842Val) for eight out of 10 cases and in exon 12 in two cases. All three cases in the small intestine revealed mutation of the PDGFRA gene in exon 12. We found no PDGFRA mutation in our colonic cases. PDGFRA expression was significantly correlated with mutations of the same gene (p = 0.005, Fisher’s exact test) and especially with mutations in exon 12 of the same gene (p