Histopathologic studies in Sézary syndrome and erythrodermic mycosis fungoides: a comparison with benign forms of erythroderma.

Histologic sections from eleven patients with Sézary syndrome were reviewed and compared with those of four patients with erythrodermic mycosis fungoides and twenty-four patients with a benign form of erythroderma, including fifteen patients with chronic dermatitis, four with a generalized drug eruption, and five with an erythrodermic psoriasis. The most important discriminating histologic feature in patients with Sézary syndrome was the presence of a monotonous bandlike or perivascular infiltrate in the papillary dermis, mainly composed of large cerebriform-mononuclear cells, as seen in seven of eleven Sézary syndrome patients. Pautrier's microabscesses were observed in seven of eleven Sézary syndrome patients, two of four patients with erythrodermic mycosis fungoides, but not in any of the patients with a benign form of erythroderma; their presence was therefore considered a reliable criterion in differentiating erythrodermic cutaneous T cell lymphoma from benign forms of erythroderma. However, features of chronic dermatitis were often found superimposed on those of Sézary syndrome and were even predominating in four of eleven Sézary syndrome patients. Moreover, four patients with a benign form of erythroderma showed a histologic picture suggestive of cutaneous T cell lymphoma. Therefore, in dubious cases repeated skin biopsies, additional investigations of lymph nodes and peripheral blood, and careful follow-up are mandatory for the achievement of a correct diagnosis.