gastric inﬂammatory fibroid polyp
Monday 12 March 2012
inﬂammatory fibroid polyp of the stomach
Inﬂammatory ﬁbroid polyps (IFPs) affect all areas ofthe GI tract.
Most lesions develop in adults, although some occur in children.
The average patient is 63 years old.
IFPs may remain asymptomatic or cause abdominal pain due to gastric outlet obstruction.
The lesions are reactive in nature.
Associated lesions include HP gastritis, gastric ulcer, adenoma, or carcinoma.
Grossly, IFPs present as sessile, ﬁrm, gray-tan polypoid or semi-pedunculated lesions that can be solitary or multiple.
Most lesions arise in the antrum, ranging in size from > 1 to 12 cm.
IFPs originate in the submucosa, are usually covered by normal mucosa, and grossly mimic leiomyomas or GI stromal tumors.
The mucosa overlying the polyp iseroded in approximately a quarter ofthe cases.
The lesions extend into the muscularis propria and may reach the serosa.
Histologically, IFPs consist of loosely structured stromal tissue.
The predominant cell type consists of spindled ﬁbroblast-like cells intermingled with inﬂammatory cells and proliferating vessels, arranged in an edematous stroma.
Whorls of ﬁbroblasts or myoﬁbroblasts surround thin-walled vessels in a concentric or onion skin–like fashion.
Vascularity and cellularity vary and may be striking.
Proliferating cells appear uniform and contain abundant cytoplasm and pale spindle-shaped nuclei.
Varying numbers of eosinophils and lymphocytes inﬁltrate the tissues.
The numerous vessels vary in their appearance and some appear thickened with hyalinized walls.
Multinucleated giant cells can be present.
IFPs gradually merge into the surrounding tissues.
The lesions evolve through several stages.
The nodular stage (average size 0.4 cm) contains nodules of immature ﬁbroblasts in a loose myxoid stroma.
The ﬁbrovascular stage (average size 1.5 cm) demonstrates concentric aggregations of mature ﬁbroblasts with endothelial proliferation and eosinophilic inﬁltrates.
In larger polyps (average size 4.8 cm), the histologic pattern evolves into the scleroticor edematous stage by either collagenization or vascular compromise.
The differential diagnosis of this lesion includes eosinophilic gastroenteritis, which typically affects younger patients and is characterized by diffuse eosinophilic inﬁltrate that may involve long bowel segments as opposed to beingrelatively restricted lesions.
Additionally, there is peripheral eosinophilia, and the lesions of eosinophilic gastroenteritisdo not show the marked ﬁbroblastic or vascular proliferationseen in IFPs.
Other entities in the differential diagnosis include GI stromal tumors (GISTS) and other mesenchymal lesions.
The spindle cells in IFPs are diffusely immunoreac-tive for vimentin and CD34.
They may be focally positive forhistiocytic makers.
They may show focal immunoreactivity for alpha smooth muscle actin.
Cytokeratin, desmin, S100, factorVIII, and Ki67 are negative in the spindle cells.