Inflammatory Fibroid Polyp of the Gallbladder Bearing a Platelet-Derived Growth Factor Receptor Alpha Mutation

Abstract

The inflammatory fibroid polyp (IFP) is a benign lesion occurring in the digestive tract, mostly in the stomach and small bowel, composed of fibrovascular tissue infiltrated by inflammatory cells including eosinophils and mastocytes. Its pathogenesis has been controversial (reactive versus neoplastic). The recent finding of mutations in platelet-derived growth factor receptor α (PDGFRA) in most gastric and small intestinal IFPs supported their neoplastic etiology, moreover helping in their differential diagnosis. In the only gallbladder IFP reported so far, the diagnosis was based on morphologic and immunohistochemical grounds, which in current standards would probably be considered not fully conclusive. Conversely, the gallbladder IFP we report shows typical pathologic features supported by a PDGFRA mutation, similar to its usual gastric and small intestinal counterparts, constituting the first report of an unequivocal IFP at gallbladder level. Thus, IFPs must be considered in the differential diagnosis of gallbladder mesenchymal masses, and genetic analysis of PDGFRA is a helpful tool for this purpose.

Unusual focal keratin expression in plexiform angiomyxoid myofibroblastic tumor

“…[ 34 ] Inflammatory fibroid polyps, although often arising in the gastric antrum, rarely grow deeper than submucosa, typically feature CD34+ spindle cells arranged in an onion-skin pattern around blood vessels, are rich in eosinophils and are often PDGRA mutant. [ 40 ] Schwannomas, although often displaying areas with a loose texture (so-called “Antoni B areas”) and sometimes featuring a plexiform architecture, often exhibit peripheral lymphoid aggregates and are consistently intensely and diffusely S100+. Inflammatory myofibroblastic tumors feature a relevant inflammatory infiltrate which, together with the loosely arranged myofibroblasts in an edematous myxoid background, simulates granulation tissue; moreover, about half of cases display cytoplasmic positivity for ALK protein.…”

PDGFRA-mutant syndrome

“…KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12, 14, and 18) genes were amplified using the same primers and PCR conditions described elsewhere. [16][17][18] Further details are reported in Supplementary Materials and Methods.…”

Telocytes are the physiological counterpart of inflammatory fibroid polyps and PDGFRA‐mutant GISTs

“…No physiological counterpart has hitherto been described for IFPs, although it has been suggested that they may develop from PDGFRA‐positive mesenchymal cells found along the villus membrane in the small intestine 2, 4. Conversely, GISTs as a whole are commonly considered to be related to interstitial cells of Cajal (ICCs) 5.…”