Mycosis Fungoides: A Dermatological Masquerader
Mycosis fungoides (MF), a low-grade lymphoproliferative disorder, is the most common type of cutaneous T-cell lymphoma. Typically, neoplastic T cells localize to the skin and produce patches, plaques, tumours or erythroderma. Diagnosis of MF can be difficult due to highly variable presentations and the sometimes nonspecific nature of histological findings. Molecular biology has improved the diagnostic accuracy. Nevertheless, clinical experience is of substantial importance as MF can resemble a wide variety of skin diseases. We performed a literature review and found that MF can mimic >50 different clinical entities. We present a structured framework of clinical variations of classical, unusual and distinct forms of MF. Distinct subforms such as ichthyotic MF, adnexotropic (including syringotropic and folliculotropic) MF, MF with follicular mucinosis, granulomatous MF with granulomatous slack skin and papuloerythroderma of Ofuji are delineated in more detail.

Mycosis fungoides (MF), a low-grade lymphoproliferative disorder, is the most common type of cutaneous T-cell lymphoma. Typically, neoplastic T cells localize to the skin and produce patches, plaques, tumours or erythroderma. Diagnosis of MF can be difficult due to highly variable presentations and the sometimes nonspecific nature of histological findings. Molecular biology has improved the diagnostic accuracy. Nevertheless, clinical experience is of substantial importance as MF can resemble a wide variety of skin diseases.

Diagnosis of MF is based on a combination of clinical presentation, histopathology and gene rearrangement. None of these factors exclusively determines the diagnosis. Histologically, MF is characterized by the presence of large atypical lymphocytes, a lymphocytic infiltrate in the papillary dermis and thickened collagen fibres. However, in early MF not all of these pathological findings are present and distinction from an inflammatory infiltrate is often difficult. Detection of a monoclonal T-cell infiltrate is not lymphoma specific. Positive polymerase chain reaction (PCR) results are also found in diseases such as psoriasis, pityriasis lichenoides et varioliformis acuta (PLEVA) and lichen ruber. Thus clinical presentation is a major factor determining the diagnosis.