Background/Purpose: Focus score (FS) remains the key element for the histological diagnosis of pSS; nonetheless, additional parameters have been proposed for clinical trials including the analysis of ectopic lymphoid structures (ELS) and the percentage of lymphocytic infiltration. Relatively few information are available regarding the feasibility and the usefulness of these additional histomorphological parameters in improving the diagnostic assessment of pSS in daily clinical practice.

Methods: Consecutive minor salivary gland biopsies (MSGBs) were collected and centralized to the same Pathology Unit from January 1st 2017 to January 1st 2020. An expert pathologist evaluated the samples focusing on: glandular tissue areas, assessment of focal lymphocytic sialoadenitis (FLS) versus non-specific chronic sialoadenitis (NSCS), number of foci, presence of ELS and. the percentage of lymphocytic infiltration (area of lymphocyte infiltration / total assessed surface area).

Results: We collected 267 MSGBs: 79 (29.6%) presenting a FLS with a FS≥1, 50 (18.7%) with a 0< FS< 1 and 114 (42.7.8%) with a NSCS. Moreover, the area of 24/267 (9%) further biopsies was lower than 4 mm2 and those samples were read only according to the Chisolm and Mason grading. The diagnosis of pSS was confirmed in 123 cases (46.1%). A FS≥1 was detected in 76/123 (61.8%) pSS patients and in 3/144 (2.1%) of no-SS patients, a 0< FS< 1 was observed in 13/123 (10.6%) pSS patients and in 37/144 (25.7%) no-SS patients, and a NSCS was found in 14 (11.4%) pSS patients and in 100/144 (69.4%) (p=0.000). Therefore, the FS did not support the diagnosis of pSS in 47/123 (38%) cases. In those samples with a 0< FS< 1 or with an uncertain FS due to an area lower than 4 mm2, the percentage of lymphocytic infiltration appeared significantly higher in pSS patients with respect to patients with no-SS (9.8% ± 4.1% vs 5.2% ± 3.6%, p=0.01) and correlated with anti-Ro/SSA positivity (r=0.443, p=0.02). ELS were present in the 30% samples and correlated with several ESSDAI domains including: lymphadenopathy, glandular, haematological and biological (p< 0.05). ELS correlated with the percentage of infiltration (r=0.733, p=0.001) highlighting the critical role of the size of the foci besides their numbers in determining the complexity of the infiltrate.

Conclusion: The percentage of lymphocytic infiltration and the assessment of ELS may provide complementary information to improve the diagnostic assessment of patients with suspected pSS, particularly in patients with a 0< FS< 1. Moreover, additional histomorphological parameters may also contribute to the identification of patients subgroups with more homogeneous glandular and extra-glandular manifestations.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/re-evaluation-of-the-extent-of-lymphocytic-infiltration-may-improve-the-diagnostic-accuracy-of-lip-biopsy-in-primary-sjogrens-syndrome-pss/