Expression of Ki-67 in Psoriasis and Other Psoriasiform Dermatitis

Background: Psoriasis is a chronic immune-mediated inflammatory skin disorder characterized by epidermal hyperproliferation and abnormal keratinocyte differentiation. Several dermatoses may exhibit similar clinical and histopathological features and are collectively referred to as psoriasiform dermatitis, making accurate diagnosis challenging in some cases. Ki-67 is a well-known marker of cellular proliferation that reflects epidermal growth activity. The present study aimed to evaluate the immunohistochemical expression of Ki-67 in psoriasis and compare it with other psoriasiform dermatoses. Methods: This cross-sectional comparative study was conducted on 60 skin biopsy specimens, including 30 cases of psoriasis and 30 cases of other psoriasiform dermatoses. Histopathological evaluation was performed using hematoxylin and eosin staining. Immunohistochemical staining for Ki-67 was carried out on formalin-fixed paraffin-embedded tissue sections. The Ki-67 labeling index was calculated as the percentage of positively stained nuclei among 1000 suprapapillary keratinocytes. Statistical analysis was performed using an independent sample t-test. Results: The mean Ki-67 labeling index was significantly higher in psoriasis (27.35 ± 9.66%) compared with psoriasiform dermatoses (9.78 ± 4.59%). The difference between the two groups was statistically significant (t = 8.99, p < 0.001). Most psoriasis cases showed Ki-67 expression within the 20–30% range, whereas the majority of psoriasiform dermatitis cases demonstrated labeling indices below 10%. Conclusion: Ki-67 immunostaining demonstrates significantly increased epidermal proliferative activity in psoriasis compared with other psoriasiform dermatoses. Therefore, assessment of the Ki-67 labeling index may serve as a useful adjunct to routine histopathology in differentiating psoriasis from other psoriasiform dermatoses, particularly in diagnostically challenging cases.