title: Endoscopic ultrasound guided fine needle aspiration biopsy of autoimmune pancreatitis: diagnostic criteria and pitfalls.
abstract: Autoimmune pancreatitis (AIP) is a benign inflammatory disease of the pancreas that mimics pancreatic malignancy both clinically and radiologically. The fine needle aspiration biopsy (FNAB) features of AIP have not previously been documented. We report our experience with AIP, highlight pitfalls, and perform a comprehensive analysis of the cytomorphologic features of this condition. We identified 16 patients with AIP, initially evaluated by endoscopic ultrasound (EUS)-guided FNAB, 11 of whom subsequently underwent a pancreatoduodenectomy. We compared these to a cohort of EUS-guided aspirates from ductal carcinoma of the pancreas (n = 16) and chronic pancreatitis, not otherwise specified (NOS) (n = 19). On all 51 cases, we semiquantitatively evaluated presence and atypia of ductal cells, presence and cellularity of stromal fragments, and inflammatory cells, type and distribution. Fifty percent (8 of 16) of the AIP cases presented as obstructive jaundice. EUS and CT scan showed mass lesions in 10 and 6 cases, respectively. There were three false-positive cytologic diagnoses, an adenocarcinoma, a solid-pseudopapillary tumor and a mucinous neoplasm. Ductal epithelium was inconspicuous and was seen in 6 cases. The FNAB samples showed background lymphocytes in three AIP cases, a feature absent in the control cohort. Stromal fragments with embedded lymphocytes (greater than 30 per 60x) were seen in 37.5% of AIP cases and only rarely with adenocarcinoma (12.5%) and pancreatitis, NOS (0%). The cellularity of stromal fragments was significantly higher in AIP than in the control group. The presence of stromal fragments of high cellularity with a lymphoid infiltrate in conjunction with clinical and radiology findings could potentially both establish a diagnosis of AIP and exclude carcinoma, thus preventing pancreatic resection.
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Boston, MA, USA. vdeshpande@partners.org
authors.forename: Vikram
authors.initials: V
authors.lastname: Deshpande
authors.forename: Mari
authors.initials: M
authors.lastname: Mino-Kenudson
authors.forename: William R
authors.initials: WR
authors.lastname: Brugge
authors.forename: Martha B
authors.initials: MB
authors.lastname: Pitman
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernandez-del Castillo
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Warshaw
authors.forename: Gregory Y
authors.initials: GY
authors.lastname: Lauwers
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D044963:Biopsy, Fine-Needle / Q000379:methods*; D002908:Chronic Disease; D019160:Endosonography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D010195:Pancreatitis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology