Comparison of morphological, immunohistochemical, and molecular genetic features of inflammatory fibroid polyps (Vanek´s tumors)

Abstract

Vanek´s tumor (inflammatory fibroid polyp) is a rare benign lesion occurring throughout the digestive tract. Histologically, two patterns can be recognized. Classical Vanek´s tumor contains concentric formations of proliferating spindle cells which are CD34 positive. Atypical, inflammatory pseudotumor-like Vanek´s tumor lacks concentric formations and is CD34 negative. Recently, mutations in platelet-derived growth factor receptor alpha (PDGFRA) were reported in gastric and small intestinal Vanek´s tumors. In this study, KIT exons 9, 11, 13, and 17, PDGFRA exons 12, 14, and 18, and a part of exon 15 BRAF for point mutation V600E were screened in 23 cases of Vanek´s tumor, both classical (n = 16) and inflammatory pseudotumor-like (n = 7). No mutations in all analyzed exons of KIT and BRAF and in exon 14 of PDGFRA were detected. Six Vanek´s tumors harbored activating mutations in PDGFRA exons 12 (n = 5) and 18 (n = 1), respectively: S566_E571delinsK (n = 1), S566_E571delinsR (n = 4), and D842 del (n = 1). The mutations were detected in the classical (n = 5), as well as inflammatory pseudotumor-like (n = 1) Vanek´s tumors. The results of this study suggest that the two morphological patterns of Vanek´s tumor more probably represent only variants of one type of tumor than two different lesions. Furthermore, BRAF mutations were not shown to drive growth of PDGFRA wild-type Vanek´s tumors.