Diagnostic utility of Ki-67 and Cyclin D1 immunostaining in differentiation of psoriasis vs. other psoriasiform dermatitis.
BACKGROUND
Differentiation of psoriasis from non-psoriasis psoriasiform dermatitis (NPPD) may be difficult for dermatopathologists, as lack of distinctive histopathological features in a subset of cases may cause confusion in diagnosis.


OBJECTIVE
As the prototype of psoriasiform dermatitis, psoriasis is a hyperproliferative skin disorder with increased epidermal turnover compared with NPPD, we investigated the role of proliferation markers, Ki-67 and Cyclin D1 as diagnostic tools to differentiate psoriasis from other psoriasiform dermatitis.


METHODS
Histopathological specimens of psoriasis (n = 35) and NPPD (n = 36, 14 pityriasis rubra pilaris, 12 pityriasis rosea and 10 lichen simplex) cases were reviewed and immunohistochemically stained for Ki-67 and Cyclin D1. Ki-67 and Cyclin D1 positive cells were counted for suprabasal, and total epidermal immunostaining per mm(2).


RESULTS
Suprabasal and total epidermal cell counts for Ki-67 were found to be significantly higher in the psoriasis group compared with the NPPD group (p < 0.05). An important and interesting feature was the presence of a cut-off value for the suprabasal/total epidermal cell count ratio of 75% for Ki-67 immunostaining, which was higher in all patients having psoriasis (range, 77.1% - 92.4%) and lower in all NPPD cases (range, 21.0% - 73.3%). However, suprabasal Cyclin D1 cell counts were higher in the psoriasis group compared with the NPPD group (p < 0.05), total epidermal Cyclin D1 cell counts were not statistically significant in either group (p = 0.167), and a cut-off value for suprabasal/total epidermal cell count ratio to distinguish these two entities was not detected using this immunostain.


CONCLUSIONS
We suggest that Ki-67 is a more sensitive marker than Cyclin D1 in terms of having a cutoff value of 75% for the suprabasal/total epidermal immunoreactive cell count ratio, which we believe could be useful for dermatopathologists in differentiating psoriasis from other psoriasiform dermatitis.
Department of Dermatology, Acibadem University School of Medicine, Istanbul, Turkey.
Engin
E
Sezer
Department of Dermatology, Dermatologikum, Hamburg, Germany.
Almut
A
Böer-Auer
Department of Pathology, Acibadem University School of Medicine, Istanbul, Turkey.
Emel
E
Cetin
Department of Pathology, Acibadem University School of Medicine, Istanbul, Turkey.
Fatma
F
Tokat
Department of Dermatology, Acibadem University School of Medicine, Istanbul, Turkey.
Emel
E
Durmaz
Department of Dermatology, Acibadem University School of Medicine, Istanbul, Turkey.
Sedef
S
Sahin
Department of Pathology, Acibadem University School of Medicine, Istanbul, Turkey.
Umit
U
Ince
Cyclin D1; Ki-67; proliferation; psoriasiform dermatitis; psoriasis