The role of salivary gland histopathology in primary Sjögren's syndrome: promises and pitfalls.

The formation of lymphomononuclear cell infiltrates organising as periductal infiltrates in the salivary glands of patients with primary Sjögren's syndrome (pSS) is one of the hallmarks of the disease. Historically, the clinical role of salivary gland histopathology, most commonly performed on labial salivary gland biopsies, has been confined to the clinical classification and diagnosis of pSS whereby according to the ACR-EULAR a positive histopathology finding is a requirement for the diagnosis of pSS in the absence of anti-Ro/SSA antibodies. In recent years, further understanding of the heterogeneity of the immune cell infiltration and organisation within the salivary glands of pSS patients and its correlation with clinical manifestations of the disease has led to propose salivary gland histopathology as a novel tool able to identify patients at higher risk of developing more severe extraglandular manifestations and lymphoma. Furthermore, recent clinical developments in ongoing randomised clinical trials with novel biologics in pSS have focused on salivary glands histopathology to inform on patients stratification based on target validation, proof of drug efficacy and mechanisms of response/resistance to therapy. However, lack of standardisation of methodology and analysis has hindered the reproducibility of data from different groups and no definitive evidence in support of the use of salivary glands histopathology to inform clinical management of patients with pSS has been provided. In this review, we summarise recent evidence highlighting the promises and pitfalls of salivary glands histopathology in pSS emphasising the need for an international consensus on standardisation of methodology with validation in large prospective multicentre initiatives.