Attempts to enhance light microscopic diagnosis of cutaneous T-cell lymphoma (mycosis fungoides)

Precise pathologic criteria for the diagnosis of mycosis fungoides (MF) remain controversial. With the use of a specific counting technique and defined criteria for cell types, we attempted to differentiate between a series of slides from patients with eczematous dermatitis, large plaque parapsoriasis, and atypical dermatitis with features that suggest MF, the plaque stage of MF, and the tumor stage of MF. This could not be done on the basis of cellular density in a defined field in the papillary dermis or on the basis of the percentage of atypical lymphocytes in the fields counted. Furthermore, individual investigator variance was shown to be highly significant despite efforts to minimize this factor.