Suprabasal mitotic index: A cell kinetic aid in psoriasis diagnosis

Abstract

Background: Psoriatic cell kinetic studies attribute psoriatic hyperplasia to increased germinative cell layer and increased mitotic rate causing rapid cell turnover, resulting in suprabasal mitotic activity. The significant Ki-67 and p53 positivity in psoriatic suprabasal layers as opposed to basal layers in normal skin corroborates this finding. Morphology holds importance in differentiating psoriasis among plaque forming lesions as they clinically mimic each other. In this study, the significance of morphologically derived suprabasal mitotic index was evaluated in the diagnosis of psoriatic lesions.Methods: H and E stained paraffin sections of histopathology confirmed cases of psoriasis and its variants (n = 52) were retrieved from archives and studied. For comparison, control group (n = 30) comprising normal skin and other plaque lesions was used. Suprabasal mitoses/100 basal keratinocytes were calculated in both groups and evaluated using Student's t-test and receiver operator characteristics. Results: The suprabasal mitotic index was significantly higher in psoriatic lesions as compared to controls (P < 0.001) with lower counts in palmoplantar psoriasis (n = 14). The cutoff of suprabasal mitoses for non-palmoplantar psoriasis was 1/100 keratinocytes with sensitivity, specificity, positive, and negative predictive value of 94.9%, 86.7%, 90.2%, and 92.9%, respectively. The diagnostic accuracy was 91.3%. Palmoplantar psoriasis had comparatively lower values and a diagnostic accuracy of 70.45%. Conclusion: The morphological evaluation of suprabasal mitoses is a reliable and cost-effective cell kinetic tool in diagnosing psoriasis and its variants. This will aid in the differential diagnosis of plaque forming lesions.