Utility of Endoscopic Ultrasound-Guided Fine-Needle Aspiration and Biopsy for Histological Diagnosis of Type 2 Autoimmune Pancreatitis

Abstract

In Japan, type 1 autoimmune pancreatitis (AIP) is the most common type of AIP; type 2 AIP is rare. The aim of this study was to clarify the usefulness of endoscopic ultrasound-guided fine-needle aspiration and biopsy (EUS-FNAB) for the diagnosis of type 2 AIP. We analyzed the tissue specimens of 10 patients with suspected type 2 AIP who underwent EUS-FNAB at our hospital between April 2009 and March 2021 for tissue volume and histopathological diagnostic performance. The male-to-female ratio of the patients was 8:2, and the patient age (mean ± standard deviation) was 35.6 ± 15.5 years. EUS-FNAB provided sufficient tissue volume, with high-power field >10 in eight patients (80.0%). Based on the International Consensus Diagnostic Criteria (ICDC), four patients (40.0%) had histological findings corresponding to ICDC level 1, and five patients (50.0%) had histological findings corresponding to ICDC level 2. The results of this study show that EUS-FNB can be considered an alternative method to resection and core-needle biopsy for the collection of tissue samples of type 2 AIP.

Clinical features and long‐term outcomes of patients with type 2 autoimmune pancreatitis

“…EUS‐guided FNA or FNB appear to have limitations in achieving a definitive diagnosis in these patients. Based on the limited published reports, a definitive histological diagnosis is achieved after EUS guided tissue acquisition with FNA or FNB in only 40% of patients 12,17 …”

“…Based on the limited published reports, a definitive histological diagnosis is achieved after EUS guided tissue acquisition with FNA or FNB in only 40% of patients. 12 , 17 …”

“…No significant differences have been described in a retrospective study from US comparing 31 patients with a definitive diagnosis and 12 patients with a probable diagnosis of type 2 AIP 10 . Moreover, the literature suggests that definitive diagnosis based on EUS‐guided tissue acquisition might be challenging 12,13 . The clinical onset is mainly characterized by acute pancreatitis (AP; >50%) and rarely by jaundice (<25%), which is significantly different compared to type 1 AIP, mostly characterized by jaundice 4,9–11 .…”

“… 10 Moreover, the literature suggests that definitive diagnosis based on EUS‐guided tissue acquisition might be challenging. 12 , 13 The clinical onset is mainly characterized by acute pancreatitis (AP; >50%) and rarely by jaundice (<25%), which is significantly different compared to type 1 AIP, mostly characterized by jaundice. 4 , 9 , 10 , 11 Steroid responsiveness is observed in all patients and the risk of recurrence is quite low.…”

Type 2 autoimmune pancreatitis associated with ulcerative colitis

“…Several studies have noted that pancreatic tissue from IgG4-related AIP, which is type 1 AIP, contains NETs ( 14 , 108 , 109 ), and NETs-related proteins are overexpressed in the inflamed colon of UC patients ( 107 ). Although there are no reports of NETs associated with type 2 AIP, the histological feature of type 2 AIP is granulocytic epitheliopathy ( 110 ), so it is reasonable to speculate that NETs might play a role in type 2 AIP–UC. In addition, alterations in the composition and function of the intestinal microbiome (also known as intestinal dysbiosis) have been associated with digestive disorders ( 111 , 112 ), and the role of intestinal dysbiosis in the pathogenesis of ulcerative colitis has been widely recognised ( 113 , 114 ).…”