PROLIFERATIVE ACTIVITY OF EPIDERMAL AND DERMAL T-LYMPHOCYTES IN MYCOSIS-FUNGOIDES

Background: Mycosis fungoides (MF) is histologically characterized by an accumulation of T lymphocytes (T cells) in both epidermis and dermi s. However, the mechanism of the formation of Pautrier's microabscess or the maintenance of the epidermal T cells has not yet been clarified . Objective: The rate of proliferation of these T cells was investigat ed. Methods: The formalin-fixed, paraffin-embedded sections from 9 cas es of patch/plaque stage MF were immunostained with proliferating cell nuclear antigen (PCNA). Results: The PCNA-positive T cell nuclei were found both in the epidermis (including Pautrier's microabscesses) and dermis in all the specimens, The mean PCNA indices of the T cells wer e 20.2 +/- 10.6% (mean +/- SD) within the epidermis and 16.8 +/- 6.5% in the dermis, which was not statistically significantly different (p > 0.05). The ratio of the PCNA index between the epidermis and dermis was 1.3 +/- 0.6, which was not apparently correlated with the duration of the disease (8.4 +/- 5.1 years). Conclusion: These findings sugges ted that in situ proliferation might contribute to the epidermal T cel l population resulting in the formation of Pautrier's microabscesses a nd an increase in dermal T cell volume during the course of the diseas e.