Molecular Diagnosis Of Mycosis Fungoides With Rearrangement Of T Cell Receptor

Objective:To detect the rearrangement of T cell receptor(TCR)gene for the diagnosis of mycosis fungoides(MF).Mycosis Fungoides is a low maliganent cutaneous T cell lymphoma,which has a variety of manifestation.It can be divided into 3 stages,including patche stage,plaque stage,and tumor stage.It can not be diagnosed easily by Histopathology until plaque stage.The presence of intraepidermal collections of atypical cells(Pautrier microabscesses)is a highly characteristic feature.In tumor stage,the dermal infiltrates become more diffuse. The tumor cells increase in number and size,showing variable proportions of small, medium-sized,to large cerebriform cells,blast cells with prominent nuclei,and intermediate forms.The manifestations of mycosis fungoides in its early stage may mimic clinically and histologically those of many benign inflammatory dermatoses.Therefore,the diagnosis of mycosis fungoides remains a major challenge for dermatologists and dermatopathologists.Although immunochemistory is an assistant method to detect the T-cell differentiation antigen,weather the lesion is benign or maliganent is hard to determine.The main character of the maliganent lymphocytes proliferation is clonal,which is manifested by clonal rearrangement of T cell receptor in T cell lymphoma.PCR is an available and simple method for detecting gene rearrangement because TCR gene rearrangement structure is simple and is almost present in all T lymphoma.Methods:We used one-step method to extract DNA from formalin-fixed(10%)and parafin-embedded tissue blocks.61 cases of mycosis fungeides(MF),9 of subacute dermatitis,8 of lichen planus,7 of guttate parapsoriasis,7 of parapsoriasis varioliformis and 20 of normal skin were included in this stady.The TCR gene rearrangement was detected with polymerase chain reaction and agrose electrophorcsis.Results:The second primer and the third primer can not be used,x~2 is 0.000(p＞0.05)and 0.127(p＞0.05)respectively.34 cases were positive in the first primer,12 cases were positive in the fourth primer,4 cases were positive in the first and second primer at the same time.So clear clonal TCR gene rearrangements were detected in 50 of 61 MF cases(82.0%)and 13 of 31 cases control groups(41.9%)by PCR(x~2=15.260,P=0.000).Conclusion:1.The DNA extracted from parafin-embedded specimens with one-step method should be used as template to detect TCR rearrangement with PCR.2.The histopathologic features are not diagnostic in erythema stage.It's easier to diagnosis plaque stage and tumor stage MF by pathology.3.Clear clonal TCR gene rearrangements were detected in 50 of 61 MF cases (82.0%)by PCR,the positive rate is high.4.There are some positive cases in control group,especially it is so high in subacute dermatitis.So it is possible to have some false positive cases.5.This method should be an assistant way to diagnosis mycosis fungoids,but it should be combine with clinical manifestation and histopathology.