Enhancing diagnostic precision in psoriasis skin lesions: The role of ki-67 and a three-tier grading approach

Objectives: To evaluate the diagnostic utility of Ki-67 expression in distinguishing psoriasis from nonpsoriatic psoriasiform dermatoses (NPPD) and to establish a cutoff value that supports diagnosis alongside histopathological features and to assess and categorize psoriasis and NPPD based on histomorphological characteristics and the proportion of inflammatory cells using a three-tier histological grading approach. Materials and Methods: This study was conducted over a year, incorporating retrospective data from 6 months and prospective data collected between February 2024 and June 2024. A total of 32 cases were included, comprising 20 cases of psoriasis and 12 cases of NPPD. All skin biopsies were graded using a three-tier histological grading, and Ki-67 immunohistochemistry (IHC) was performed for each case. The results were then compared to assess diagnostic utility. Statistical analysis: The results were statistically analyzed using the Chi-square test, and analysis of variance variables assessed for their association with Ki-67 expression, including histopathological features such as hyperkeratosis, parakeratosis, regular acanthosis, hypo- or agranulosis, and the grade of inflammatory cell infiltrate. Both the percentage and intensity of Ki-67 expression were compared between psoriasis and NPPD to evaluate their diagnostic utility. Results: In the diagnosis of psoriasis and psoriasiform lesions, Ki-67 demonstrated a wide diagnostic cutoff range. In our study, Ki-67 immunohistochemistry showed that all 20 psoriasis cases exhibited Ki-67 expression with more than 60% positivity. In contrast, the majority of psoriasiform cases were negative for Ki-67, with only 16% showing expression above 50%, indicating a statistically significant difference ( P < 0.05). Histopathological grading using our three-tier histological grading revealed that confluent parakeratosis, regular acanthosis, and agranulosis were significantly more common in psoriasis cases. Minimal dermal inflammation was also more frequently observed in psoriasis. However, hyperkeratosis did not show a significant difference between the two groups. Conclusions: This study emphasizes the utility of our structured three-tier histological grading combined with Ki-67 immunostaining in distinguishing psoriasis from NPPD. A Ki-67 cutoff of 60% and above may enhance diagnostic accuracy in cases with overlapping clinical and histological features.