Unilesional mycosis fungoides. A new clinicopathologic entity?

The term unilesional mycosis fungoides (MF) has been recently introduced by some authors to define an uncommon variant of MF which is clinically characterized by a solitary lesion and a favorable prognosis despite its clinical and histological resemblance to typical MF. Two patients with a single erythematous-scaly plaque located on the left mammary region and on the upper part of the right thigh, respectively are presented. Histological examination showed the same features in both patients. A band-like infiltrate, composed of small and medium-sized atypical lymphocytes with cerebriform nuclei was located in the papillary dermis. Areas of epidermotropism were also present. Immunohistochemical studies showed positive staining of neoplastic cells for T-cell associated markers (CD3, CD4, CD45RO). Molecular analysis revealed a TCRγ monoclonal rearrangement in both cases. Staging procedures in both patients were negative. Patients were treated with low-dose systemic recombinant interferon α2b achieving complete clinical remission after 12-month therapy. After a 2-year follow-up period, no recurrence or progression of the disease developed. Conclusions. The appearance with a solitary lesion and the absence of disease progression in a 2-year period, as observed in our patients, are consistent with the diagnosis of unilesional mycosis fungoides. However, the unusual occurrence of MF as a solitary lesion and the lack of long-term follow-up do not allow a definite nosological classification of this MF variant.