Abstract: Abstract Objective: To study the characteristics of the cutaneous pseudo lymphomas（CPL） in histopathology, immunohistochemistry and gene rearrangement. Methods: Using HE staining method to proceed histopathological examination on 28 paraffin-embedded CPL tissues. The expression of CD3、CD20 and CD45RO in these tissues is also detected by two-step immunohistochemistric method and the gene rearrangement of TCR-γand IgH are tested by Polymerase Chain Reaction（PCR）. 10 cases of lichen planus（LP）lesions as control group are chosen in these experiment . Results: In the aspect of histopathology, the tissues of 28 CPL skin lesion in patie nt group revealed plenty of lymphocytic infiltration in the shallow lay of dermis. The result of immunohistochemistry indicate that among 28 cases in patient group,there were 13 cases with mainly positive expression of CD3 and CD45RO which have no statistical significance compared with the control group. Other 15 cases have the mainly positive expression of CD20 and are statistically different compared with the control group. On the other hand, none TCR-γgene rearrangement show positivity. 20 cases of rearrangement express negative, 8 cases appear smear band. For the gene rearrangement of IgH, most of them expressed negative except 1 case appearing smear band. Conclusion: The partial pathological lymphoid infiltration in the CPL skin lesion are T cells with the expression of CD3 and CD45RO, while others lymphoid infiltration are B cell with the expression CD20. The detection of TCR-γand IgH gene rearrangement have a important reference value for the diagnosis of malignancy status of CPL.

Key words: cutaneous pseudolymphomas, immunohistochemistry, gene rearrangement, PCR