THU0291 IS GIANT CELL ARTERITIS REALLY GIANT CELL ARTERITIS? A HISTOLOGICAL REVIEW OF TEMPORAL ARTERY BIOPSIES FROM A UK DISTRICT GENERAL HOSPITAL
Authors: S. K. Amar, D. Christidis, G. Kousparos, M. Lloyd
Journal: Annals of the Rheumatic Diseases (2020)

Background: Despite the advent of newer imaging techniques, temporal artery biopsy (TAB) retains a key role in the diagnosis of giant cell arteritis (GCA). The classical histological description of GCA is that of granulomatous lesions characterized by a transmural inflammatory infiltrate 1 . Giant cells are typically noted in the internal elastic lamina. Vascular remodeling and structural changes are also frequently described, with intimal hyperplasia or fragmentation, fibrosis and calcifications 1 . Objectives: To identify the type and location of the inflammatory lesions in TAB-positive cases of GCA. Methods: We conducted a retrospective analysis of all TABs undertaken at our unit between 2011- 2018 with clinical record review. TABs were performed by vascular, ophthalmology and ENT teams. Results: 379 TABs were reviewed of which 68 (17.9%) were reported as positive and 10 (2.6%) were equivocal (presence of fragmentation and intimal thickening). Of the TAB-positive cases, 43 (63.2%) were greater than 1cm in keeping with the British Society for Rheumatology guidance and 65 (95.6%) were biopsies in patients on corticosteroids at the time of procedure. The following tables demonstrate the frequency of the type and location of the inflammatory lesions detected in TAB-positive cases of GCA. Type of inflammatory lesion Frequency Chronic inflammatory infiltrate (lymphocytes, macrophages, plasma cells) 66 Giant cells 41 Intimal thickening 22 Intimal fragmentation 33 Location of inflammatory infiltrate Frequency Full thickness 32 Intima only 7 Intima and Media only 3 Media only 7 Media and Adventitia only 8 Adventitia only 4 Intima and Adventitia only 3 Not recorded 4 Conclusion: Only 60% of our TAB-positive biopsies had giant cells present. Although perhaps surprisingly low, this finding is similar to other studies 1,2 . It emphasises the need to review the body of a report as well the conclusion. Other non-giant cell features present in positive reported biopsies may suggest a less certain diagnosis and prompt clinical review. There was considerable variablity in the style of reporting. With no standardised scoring system in place, the variable spectrum of inflammation and differences in reporting, there is the potential for inconsistencies amongst pathologists in interpreting and recording TAB results. Consistent reporting templates and close collaboration between rheumatologists and pathologists is needed to help correlate clinical, laboratory and imaging findings. References: [1]Cavazza A, Muratore F, Boiardi L, Restuccia G, Pipitone N, Pazzola G, et al. Inflamed temporal artery: histologic findings in 354 biopsies, with clinical correlations. Am J Surg Pathol. 2014;38(10):1360-70. [2]Hernandez-Rodriguez J, Murgia G, Villar I, Campo E, Mackie SL, Chakrabarty A, et al. Description and Validation of Histological Patterns and Proposal of a Dynamic Model of Inflammatory Infiltration in Giant-cell Arteritis. Medicine (Baltimore). 2016;95(8):e2368. Disclosure of Interests: Soha Khaled Amar: None declared, Dimitrios Christidis: None declared, George Kousparos: None declared, MARK LLOYD Speakers bureau: £700 into department fund