Clinical Characterization of Fibroblastic Polyps

Abstract

Introduction: Fibroblastic polyps (FPs) are a rare, recently described colorectal polyp subtype histologically characterized by the proliferation of bland spindled cells within the lamina propria. FPs are distinguishable immunohistochemically (IHC) from other mucosal polyps and are generally discovered incidentally. While considered benign and unassociated with polyposis syndromes, a paucity of clinical information exists regarding this polyp subtype. As a large tertiary endoscopy practice, we sought to describe our clinical experience in patients diagnosed with FPs. Methods: Cases were identified between Jan 1994 and May 2017 among patients 18-99 years of age at the time of diagnosis using an institutional pathology database. Clinical data was abstracted using existing clinical and endoscopic records. IHC was performed at the discretion of the reviewing pathologist and only those cases with compatible histology and supportive IHC (negative S-100, EMA, CD117) were included for review. Results: A total of 21 patients with a diagnosis of FP (n=32 polyps) were identified. Following diagnosis, none of the patients were found to have FPs on subsequent colonoscopies. The median age at FP diagnosis was 59 years (range 31-84) with 13 (62%) being male. A single FP was identified in all but one case; in the remaining case, 12 FPs were simultaneously diagnosed in a patient with Cowden syndrome. The median FP size was 4 mm (range 2-8 mm) while by configuration, 27 (84%) and 5 (16%) were sessile and pedunculated, respectively. FPs were predominately located in the left colon with 17 (53%), and 5 (16%) discovered in the rectosigmoid and descending colon, respectively. In 11(52%) cases, FPs were concomitantly diagnosed with other polyp subtypes including tubular adenoma with low-grade dysplasia (7/11), hyperplastic polyp (3/11), and sessile serrated adenoma (1/11). Among patients diagnosed with FPs, indications for colonoscopy varied; routine follow-up for known history of adenomatous polyps and initial colorectal cancer (CRC) screening were the most common in 9 (43%) and 6 (29%) patients, respectively. Conclusion: FPs are rare, predominately left-sided colonic polyps which vary between sessile and pedunculated configuration. Though predominately solitary, multiple FPs were observed in a patient with Cowden syndrome and no patients had FPs diagnosed on subsequent endoscopy. Further study is needed to elucidate the pathogenesis and significance of FPs.