Assessment of histologic criteria in the diagnosis of mycosis fungoides

Background The histologic diagnosis of early mycosis fungoides (MF) can be difficult to establish in many instances because the subtle changes observed in patches of MF are also present in many inflammatory dermatoses. Methods To assess the frequency and significance of many of these histologic parameters, we retrospectively reviewed 50 slides from patients with documented MF in patch, plaque, and tumor stages. The diagnosis of MF was unequivocally established either by the progression of patients to advanced stages of the disease or by indubitable histologic findings. In the second phase of the study, we compared the histologic parameters observed in 24 patch stage MF patients with those in 24 non‐MF patients. The non‐MF group were patients whose pathologic pattern was suspicious for MF, but who definitely did not have MF on clinical grounds. The two groups were matched by histologic pattern. Two different observers evaluated the slides and the intensities of 32 histologic parameters were graded on a four‐point scale to minimize the subjective variability in the histologic reports. Results On univariate analysis, the following parameters achieved significance in distinguishing MF from non‐MF: Pautrier's microabscesses, haloed lymphocytes, disproportionate epidermotropism, epidermal lymphocytes larger than dermal lymphocytes, hyperconvoluted lymphocytes in the epidermis and dermis, absence of dyskeratosis, and papillary dermal fibrosis. None of these features proved to have additional discriminating power on multivariate analysis. Conclusions The efficacy of single histologic features in the diagnosis of early MF is generally poor and, to discriminate MF from its inflammatory simulators, a combination of cytologic and architectural features must be used.