Cutaneous T-cell lymphoma: important diagnostic tools

Cutaneous T-cell lymphomas comprise a complex group of disorders with heterogeneous clinical and genotypic features. Of these, mycosis fungoides represents the most common subtype. The diagnosis of these entities remains a challenging process due to their diverse clinical presentations and subtle microscopic features. Evaluation currently relies upon clinical criteria, in combination with histochemical, immunological and molecular studies. Recent algorithms have been proposed using criteria that incorporate each of these approaches. This review will focus on tools and techniques utilized for the diagnosis of cutaneous T-cell lymphomas classified within the most recent World Health Organization/European organization for Research and Treatment of Cancer (WHO/EORTC) consensus criteria. Particular emphasis will be placed on mycosis fungoides and Sézary syndrome. Key features facilitating the clinical and microscopic interpretations will be outlined, as well as a synopsis of the advances made in the use of techniques such as immunohistochemistry, flow cytometry and gene rearrangement. We will also consider some recently reported novel approaches that explore these complex diseases at the molecular and genetic levels.