Ultrasound-guided core needle biopsy and incisional biopsy of the parotid gland are comparable in diagnosis of primary Sjögren's syndrome

Objectives: Salivary gland lymphocytic infiltrates are a hallmark of primary SS (pSS), but traditional biopsy techniques hold several disadvantages. Ultrasound-guided core needle (US-guided CN) parotid gland biopsy is minimally invasive and reliable for diagnosis of lymphoma in pSS. This proof-of-concept study aimed to explore this technique in the diagnostic work-up of pSS and is the first to address its value in a consecutive cohort independently of the presence of salivary gland swelling.

Methods: Combined incisional and US-guided CN parotid biopsy was performed in 20 patients with suspected or confirmed pSS from the Belgian Sjögren's Syndrome Transition Trial (BeSSTT). Surface area and presence of a focus score (FS) of at least one, germinal centres and lymphoepithelial lesions were recorded.

Results: Salivary gland tissue was interpretable in 19 patients. Fourteen patients had ≥4 mm2 salivary gland tissue by both techniques, in four US-guided CN biopsies salivary gland tissue was <4 mm2. Paired biopsies ≥4 mm2 displayed a concordance of 90% for FS ≥ 1. Presence of lymphoepithelial lesions and germinal centres showed absolute concordance. Of four US-guided CN biopsies <4 mm2, three interpretable incisional biopsies were available, 2/3 with perfect concordance. When including biopsies of <4 mm2 salivary gland tissue, presence of FS ≥ 1 or germinal centres gave a sensitivity of 70% in incisional and of 69% in US-guided CN biopsy.

Conclusions: US-guided CN biopsy of the parotid gland is at least equivalent to incisional biopsy of the parotid gland in the diagnostic work-up of pSS.