Inflammatory fibroid polyp of the small bowel with a mutation in exon 12 of PDGFR alpha.

Inflammatory fibroid polyp (IFP) is a benign reactive uncommon submucosal lesion of the gastrointestinal tract, the small intestine being the most common site of origin. Histologically, IFPs are characterized by spindle cells, a heavy inflammatory infiltrate including eosinophils and onion-sheet-like formation of lesional cells around blood vessels. We present a case report of an IFP harboring an activation mutation in the PDGFR alpha gene. The lesion was positive for CD34, PDGFR alpha, and p-PDGFR alpha immunostaining but was negative for c-KIT and desmin. After a sequencing analysis of KIT and PDGFR alpha, a mutation consisting of an in-frame deletion of codons 567-571 and a missense mutation in codon 566 (S566R) of PDGFR alpha was observed. This mutation could activate key cellular pathways with involvement in the pathogenesis of this entity. We concluded that more studies are necessary in order to clarify if this finding is a biologically distinct behavior or, on the contrary, represents a specific feature of the IFP.