Histopathologic Features in Urticaria and Urticarial Variants: Plasma Cells Should Be Rare

ABSTRACT Introduction Urticaria is a common cutaneous reaction pattern characterized by clinically transient edematous papules and wheals. Microscopically, intensity and predominant inflammatory cell type can vary, including lymphocytes, eosinophils, neutrophils, and mast cells. Plasma cells are rarely described within the infiltrate of urticaria, but systematic study to evaluate the frequency of this finding is lacking. Materials and Methods The institutional dermatopathology archive was searched for 2018–2023 to identify cases diagnosed as urticaria and urticarial variants; 58 consecutive cases were included. Study authors, including one board‐certified dermatopathologist, evaluated H&E slides for variation in inflammatory cells present, inflammation density/distribution, and predominant cell types. Results Fifty‐eight cases (female: 39, male: 19) were reviewed. Eleven cases (19%) showed rare, scattered plasma cells (0.02–0.09/mm 2 ). Other inflammatory cell types predominated and, like other studies, fell into lymphocytic and neutrophilic predominant categories. Inflammation density predominantly ranged from sparse to moderate, with only two cases having brisk inflammation. Conclusion This study highlights that rare plasma cells may be present in urticaria biopsies but should not be abundant or clustered.