Clinicopathological concordance across panniculitis: biopsy timing and laboratory parameters in predicting temporal variability and histopathological features in erythema nodosum.

The evolving pathological features of panniculitis make biopsy timing critical. This study explores clinicopathological concordance and the role of biopsy timing and non-invasive laboratory parameters in predicting histopathological findings in erythema nodosum (EN). Our retrospective study analysed the clinical and pathological features of all clinically suspected and/or histopathologically diagnosed panniculitis cases over a period of 3.5 years. The week of biopsy, total leukocyte count, neutrophil-to-lymphocyte ratio, neutrophil-to-monocyte ratio, erythrocyte sedimentation rate (ESR), and their impact on histopathological features were analysed. The clinicopathological concordance was 61.4% for panniculitis overall (n=69) and 66.2% for EN (n=30). Cohen's kappa showed fair agreement for EN (κ=0.318). The sensitivity of clinical diagnosis for EN was 70%, with a specificity of 64%. The odds of getting small-sized adipocytes, fat necrosis, septal fibrosis, and vasculopathic changes were 1.872, 1.565, 1.361, and 1.235, respectively, for every 1-week rise in biopsy timing. An inverse correlation was found between granuloma formation and elevated ESR (p=0.037). Recurrence of EN was significantly associated with granuloma presence (p=0.045). This study evaluates the clinicopathological concordance, sensitivity, specificity, and precision of clinical diagnoses in cases of panniculitis. This study highlights the importance of objectively understanding the temporal heterogeneity in EN's pathological features over time.