Reassessment of lymphocytic atypia in the diagnosis of mycosis fungoides

The manifestations of mycosis fungoides in its early stage may mimic clinic ally and histologically those of many benign inflammatory dermatoses, There fore, the diagnosis of mycosis fungoides remains a major challenge for derm atologists and dermatopathologists. For many years, it has been proposed th at atypical lymphocytes within the epidermis constitute one of the diagnost ic features in mycosis fungoides, Presence of dermal atypical lymphocytes r emains controversial as a diagnostic criterion. We reassessed the feasibili ty of applying lymphocytic atypia within epidermis and dermis as diagnostic criteria discriminating between mycosis fungoides and spongiotic dermatiti s, Thirty cases of mycosis fungoides and 30 cases of spongiotic dermatitis were retrieved from archival hematoxylin and eosin-stained histologic secti ons, Punch biopsy sections were examined by light microscopy; epidermal and dermal lymphocytes were photographed at 1000x (oil immersion). A total of 92 ektachrome slides (35 mM) were developed, coded, and ordered randomly, F or each slide, cells were interpreted as typical or atypical lymphocytes by seven pathologists. Atypical epidermal lymphocytes were judged to be prese nt in 9 +/- 2 out of 16 (56%) cases of mycosis fungoides photographed as co mpared with 8 +/- 3 out of 16 (50%) in spongiotic dermatitis, Dermal lympho cytic atypia was thought to be present in 14 +/- 6 out of 30 (47%) patients with mycosis fungoides, Thirteen +/- 6 out of 30 (43%) patients with non-m ycosis fungoides also displayed dermal lymphocytic atypia. No statistical s ignificance was observed in these comparisons (t test, P >.05). Furthermore , atypia of lymphocytes was deemed to be present in 41, 38, 59, 70, 23, 47, and 40 out of 92 slides examined by the investigators, suggesting that obs erver variation is a very significant factor in our present study. We concl ude that it is not possible to distinguish mycosis fungoides from spongioti c dermatitis merely based on lymphocytic atypia within epidermis or dermis.