REASSESSMENT OF HISTOLOGIC PARAMETERS IN THE DIAGNOSIS OF MYCOSIS-FUNGOIDES

The histologic diagnosis of mycosis fungoides (MF) can be difficult to establish and is based on interpretation of numerous subtle changes, most of which may be present to some degree in many inflammatory and n eoplastic cutaneous conditions. To reassess the diagnostic criteria fo r making a histologic diagnosis of MF, we retrospectively reviewed his tologic sections from 64 patients with mycosis fungoides (MF +) and co mpared the findings with sections from 47 patients who were biopsied t o exclude MF and were shown not to have the disease (MF -). Patients w ere selected as MF + or MF - independent of histologic findings based on the clinical course with at least 3 years of follow-up and immunoph enotyping results. Following patient selection, at least two observers reviewed each slide without knowledge of final diagnosis and graded t he intensity of approximately 25 histologic parameters. On univariate analysis, the following parameters were significant at beyond the p = 0.01 level: Pautrier's abscesses, haloed lymphocytes, exocytosis, disp roportionate epidermotropism, epidermal lymphocytes larger than dermal lymphocytes, hyperconvoluted intraepidermal lymphocytes, and lymphocy tes aligned within the basal layer. Haloed lymphocytes proved to be th e most robust discriminator of MF from non-MF on multivariate analysis . These findings show that whereas many previously described features do discriminate between MF and inflammatory mimics, others are much le ss specific. Furthermore, few cases demonstrate all histologic feature s; for example, Pautrier's microabscesses were seen in only 37.5% of o ur cases. We conclude that a combination of specific histologic parame ters can be used to establish a microscopic diagnosis of MF without th e necessity of confirmatory immunophenotyping in the vast majority of cases.