This is a case presentation of an Inflammatory Fibroid Polyp, a rare submucosal lesion with eosinophilic inflammatory infiltrates that can be found throughout the gastrointestinal tract. Proper diagnosis of these lesions is important for surgical planning, with a diagnosis based on histologic and immunohistochemical examination, highlighting the need for thorough investigation of duodenal lesions. A 64 year-old man presented to clinic with complaints of occasional diarrhea after ingesting milk products, as well as a five-pound unintentional weight loss in the past three weeks. He denied other GI symptoms, including nausea, vomiting, constipation, rectal bleeding, fevers, or chills. He underwent an EGD for further investigation into these symptoms, and was found to have gastritis and an 8-9 mm submucosal fundic lesion; he was then referred for endoscopic ultrasound. About one year later, he underwent a second EGD, and was found to have multiple subcentimeter polpys in the body of the stomach. During this intervening one year, he also developed a single polyp measuring 6-7 mm in his duodenal bulb, from which a biopsy was taken. The specimen was sent for analysis and pathology showed duodenal mucosa with eosinophilia (more than 50 eosinophils per high power field), and reactive lymphoid aggregate. No dysplasia or malignancy was noted. Inflammatory fibroid polyps (IFP) are exceedingly rare submucosal lesions with eosinophilic inflammatory infiltrates. Of the approximately 1,000 cases identified, only about 1% have occurred in the duodenum, with roughly 70% in the stomach. The presentations of IFPs are variable; our patient did not have worsening symptoms over the one year prior to diagnosis. Thus, histopathologic examination remains the cornerstone for diagnosis of IFP. Immunohistochemically, actin and CD34 are positive, while CD117 and S100 are negative. CD117 is a useful cell surface marker to differentiate IFP from GIST. The etiology of these polyps is still unknown, and although it is believed to be a benign process, these polyps can resemble malignant lesions and should be resected, either endoscopically or surgically, depending on the size of the lesion. Proper diagnosis of this benign lesion is essential to avoid unnecessarily wide resections, and endoscopic ultrasound can help guide pre-surgical planning.2567_A Figure 1. EGD from patient showing single polyp (6-7 mm in size) in the duodenal bulb2567_B Figure 2. Duodenal mucosa with eosinophilia (>50 eosinophils per high powered field 400x)”2567_C Figure 3. Duodenal mucosa with eosinophilia (>50 eosinophils per high powered field, 200x)