Immunohistochemical Classification Of Ipmn Obtained By Eus-Guided Microbiopsies Reveals Predominance Of The Pancreatobiliary Sybtype

Different histological subtypes of intraductal papillary mucinous neoplasms (IPMN) of the pancreas have unequal potential for malignant transformation, with pancreatobiliary subtype being associated with increased risk of high grade dysplasia and progression to malignancy. However, studies reporting this have almost exclusively examined resected specimens. Recently, procurement of endoscopic ultrasound (EUS)-guided microbiopsies from the wall of the cystic lesion has become available, allowing preoperative histopathological diagnosis with further subtyping in case of IPMN. We wanted to examine the prevalence of different subtypes of IPMN in obtained microbiopsies. Patients that underwent EUS-guided microbiopsy procedure with a histopathological diagnosis of IPMN were included retrospectively from a tertiary care center. The microbiopsies were formalin-fixed, paraffin embedded, and the sections were mounted on glass slides. Routine hematoxylin and eosin stain was used, and in case of IPMN, supplementary immunohistochemical stains were performed (S100P, MUC1, MUC2, MUC5AC, MUC6 and CDX2). Senior pathologist (JPH), specialized in pancreatic pathology examined the microbiopsy specimens. We identified nineteen cases of IPMN, all of them with low grade dysplasia. Fourteen of those (73.7%) were classified as pancreatobiliary, two (10.5%) as intestinal, two (10.5%) as mixed type and in one case (5.3%) the subtype could not be determined. Prevalence of pancreatobiliary subtype did not differ significantly between the lesions with or without worrisome features and/or high risk stigmata (p=0,754). Only three patients (15.8%) underwent surgical resection, and the microbiopsy diagnosis including the subtype was confirmed in all three cases (100%). The diagnosis of pancreatobiliary subtype did not alter the clinical management of the lesion. To our knowledge, this is the first study subtyping IPMN lesions in microbiopsy material. The high prevalence of pancreatobiliary subtype is intriguing, but does not seem to be associated with aggressive behavior in this heterogeneous cohort containing lesions without worrisome features or high-risk stigmata.Tabled 1Table 1Number of patients19Age (mean, SD)74.1 (10.6)Size of the lesion in mm (median, IQR)30.0 (20.0-40.0)Lesion characteristics:Worrisome features*10 (52.6%)High risk stigmata*2 (10.6%)No worrisome features7 (36.8%)IPMN subtypes observed:Pancreatobiliary14 (73.7%)Intestinal2 (10.5%)Mixed type2 (10.5%)Inconclusive1 (5.3%)SD, standard deviation; IQR, interquartile range; IPMN, intraductal papillary mucinous neoplasm; *According to the revised International Consensus Guidelines 2017, Tanaka et al. Open table in a new tab