Reflectance confocal microscopy as a first-line diagnostic technique for mycosis fungoides.

Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma and is a diagnostic challenge in its early stages. It often can be misdiagnosed as chronic contact dermatitis, atopic dermatitis, psoriasis, or other common dermatoses. Histologic diagnosis remains the gold standard for MF; however, in many cases repeat biopsies may be needed over time, especially in early patch stages of MF. Reflectance confocal microscopy (RCM) is a quick and noninvasive diagnostic tool that may be useful to determine an appropriate area to biopsy. We present the case of a 60-year-old man with plaque and tumor lesions clinically suspicious for MF that had originally been misdiagnosed as psoriasis. Reflectance confocal microscopy was used to evaluate for findings specific to MF and to select an appropriate biopsy site. The features noted on RCM were consistent with MF, and subsequent biopsy revealed tumor-stage disease. This article describes a unique case in which RCM was used for initial primary diagnosis of tumor-stage MF in a clinical setting. As in prior studies, our evaluation failed to identify unique RCM features specific to tumor-stage MF when compared to plaque- or patch-stage disease. Nonetheless, RCM may be useful in providing a quick noninvasive diagnosis when the clinical presentation of MF is ambiguous, especially in early lesions.