The Adequate Number of Histopathology Cross-sections of Temporal Artery Biopsy in Establishing the Diagnosis of Giant Cell Arteritis

Abstract

Purpose: To determine the appropriate number of histopathological cross-sections that are required for a conclusive diagnosis of giant cell arteritis (GCA).

Methods: In this cross-sectional study, the number of sections per slide for paraffin-embedded blocks for 100 randomly selected cases where GCA was suspected and those for negative temporal artery biopsies (TABs) were compared with the number of cross-sections per specimen for eight positive-TABs. All aforementioned examinations were conducted at our center from 2012 to 2016. Then, negative-TABs were retrieved and re-evaluated using light microscopy considering the histopathological findings of GCA.

Results: Ninety-five paraffin blocks were retrieved. The original mean biopsy length was 15.39 $\pm$ 7.56 mm. Comparison of the mean number of cross-sections per specimen for both the positive- and negative-TABs (9.25 $\pm$ 3.37 and 9.53 $\pm$ 2.46) showed that 9.87 $\pm$ 2.77 [95% confidence intervals (CI)] cross-sections per specimen were sufficient for a precise GCA diagnosis. There was no statistically significant difference in the mean biopsy length (P = 0.142) among the eight positive-TABs. Similarly, no significant difference was observed in the number of cross-sections per specimen (P = 0.990) for positive-TABs compared to those for the negative-TABs. After the retrieval of negative-TABs, the mean number of total pre- and post-retrieval cross-sections per specimen was 17.66 $\pm$ 4.43. Among all retrieved specimens, only one case (0.01%) showed the histopathological features of healed arteritis.

Conclusion: Positive-TABs did not reveal more histological cross-sections than the negative ones and increasing the number of cross-sections did not enhance the accuracy of TAB.

Keywords: Histopathology Cross-sections; Temporal Artery Biopsy; Giant Cell Arteritis.

Figure 1

(A) Healed arteritis: note the narrow lumen and minimal intramural lymphocytic infiltration, scarring, and fibrosis (asterisks) in areas with destroyed elastic lamina (short arrows) compared to the areas of intact elastic lamina (long arrows), (H&E staining $\times$40). (B) Normal artery, negative for GCA (H&E staining $\times$40). (C) Active GCA: note the obstruction of the lumen, arterial wall thickening, elastic lamina fragmentation, and intramural inflammation with multinucleated giant cells (arrow), (H&E staining $\times$100). GCA, giant cell arteritis; H&E, Hematoxylin and Eosin

Figure 2

Summary of the methods and main outcomes of the study. *There was no significant difference in the mean number of cross-sections per specimen between the positive- and original negative-TABs (P = 0.990). Based on the comparison of these two items, 9.87 $\pm$ 2.77 (95% confidence intervals) cross-sections per specimen were considered sufficient for precise results. In addition, retrieval of the original negative-TABs at multiple levels did not enhance the accuracy of TAB for diagnosing GCA. GCA, giant cell arteritis; TAB, temporal artery biopsy