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

Summary 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.