Primary Sezary Syndrome Commonly Involves Skin Without Epidermotropism

Sezary syndrome (SS) is a T‐cell lymphoproliferative disorder involving the blood, skin and lymph nodes associated with erythroderma. Other cutaneous manifestations of SS include palmoplantar keratoderma, ectropion, and alopecia. Two clinical patterns of SS can be defined: “secondary” SS arising from systemic spread of long‐standing mycosis fungoides (MF) and “primary” SS with a much shorter prodromal phase characterized by pruritus, xerosis and scaling culminating in erythroderma. Most previous studies examining the histological features of SS have not distinguished between these two different clinical patterns, and have emphasized that the histological features of SS mostly resemble those of typical MF, including epidermotropism and/or band‐like superficial dermal lymphoid infiltrates. In this study, we have concentrated on the histological findings of primary SS and correlated them with the clinical and hematologic parameters at the time of skin biopsy. We note that dermal perivascular lymphoid infiltrates predominate in a majority of primary SS cases, raising the differential diagnosis of benign dermatoses, rather than resembling the classical pattern of MF. This impression is further complicated by commonly observed epidermal changes such as spongiosis, acanthosis and parakeratosis that are likely secondary to tumor‐associated pruritus and secondary lichenification.