Expression of proliferation markers and cell cycle regulators in T cell lymphoproliferative skin disorders

Background: Abnormal cell proliferation, which results from deregulation of the cell cycle, is fundamental in tumorigenesis. Objectives: To investigate the expression of proliferation markers and cell cycle regulators in a range of T cell lymphoproliferative skin diseases. Methods: We studied skin specimens of 51 patients with parapsoriasis (PP), mycosis fungiodes (MF), or lymphomatoid papulosis (LyP). Immunohistochemistry was performed for Ki-67, proliferating cell nuclear antigen (PCNA), minichromosome maintenance protein 7 (MCM7), and p21. Results: MF with stage IIB-IV and LyP showed a significantly greater number of Ki-67-positive cells than PP (P=0.02 and 0.001) and MF I-IIA (P=0.019 and 0.003), respectively. MCM7 staining revealed significantly higher labeling indices for MF IIB-IV and LyP when compared to PP (P = 0.002 and 0.04) and MF I-IIA (P = 0.0005 and 0.01), respectively. Compared to PP and MF I-IIA, MF IIB-IV was associated with significantly higher labeling indices for PCNA (P = 0.006 and 0.0004). p21 staining was significantly increased in MF IIB-IV and LyP when compared to PP (P = 0.006 and 0.003) and MF I-IIA (P = 0.003). However, p21 staining was all in all very weak. Conclusions: Ki-67 and PCNA seem to be useful immunohistological parameters for the correlation with the clinical stage of MF In the differentiation and prognostication of T cell lymphoproliferative skin disorders, MCM7 may serve as a novel biomarker which is, in contrast to Ki-67 and PCNA, stable throughout the cell cycle. (c) 2007 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.