Background:

Mycosis fungoides (MF), a T-cell lymphoma, is the most common variant of primary cutaneous lymphomas. The discrete clinical aspect of the early patch-stage and an overlapping clinical presentation with other erythematosquamous skin diseases make the diagnosis of MF challenging. Histopathology is the gold standard for the diagnosis of MF. However, in early stages, MF can simulate inflammatory diseases, presenting reactive lymphocytes and absence of lymphocytic cytologic atypia. Consecutive biopsies are often necessary from several clinically suspect sites. Previous studies evaluated Reflectance Confocal Microscopy (RCM) as a promising tool for MF diagnosis because it offers the opportunity to analyze skin structures non-invasively at a ‘quasi-histopathologic’ resolution and to guide the most representative site for biopsy.

Case presentation:

We present a 76 years-old woman with a 5-year history of erythematous plaques and patches. She had had 5 previous skin biopsies with a pattern suggestive of nummular eczema. The history and the clinical presentation led to the suspicion of MF. RCM examination was performed and two lesions were marked for biopsy. The histopathology exam confirmed the diagnosis of MF. The patient was submitted to topical treatment with total remission of the lesions.

Conclusions:

The mean time from onset of symptoms to diagnosis is 6 years and the delay in diagnosis results in delay for adequate therapy. Therefore, the selection of the biopsy site is crucial to avoid unrepresentative samples. Mancebo et al. recently published the largest cohort of cutaneous T.cell lymphoma examined with RCM. 83 lesions were evaluated, and the authors confirmed that this image technique was effective in to guide the most representative site for the biopsy. We believe that further and larger studies will clarify it and defining a diagnostic algorithm for the RCM diagnosis of MF.