In order to characterize the benign and malignant proliferation of lymphoid cells in skin, we compared surface markers and cytoplasmic organelles of cells in cutaneous lymphoid hyperplasia (CLH), lymphomatoid papulosis (LP), mycosis fungoides (MF), Sézary's syndrome (SS) and primary cutaneous malignant lymphoma (ML). The immunohistochemical study showed cells with both T - and B-cell markers in CLH,LP and early MF, whereas cells with only the T-cell marker were seen in late MF, SS and ML. T-cells in all cutaneous lesions possessed the surface marker common to T-cells of peripheral lymph nodes, and not that of central thymus cells. Cutaneous T-cells contained clustered or scattered dense core granules. Although no specific organelles indicative of benign or malignant lymphoid proliferation were found, there were several ultrastructural features that could help identifying each form of cutaneous lymphoid lesions. These included clustered or scattered dense-core granules, the variable degree of nuclear convolutions as well as dendritic arborization, and the presence or absence of 10 nm filaments.

A case of a 77-year-old male with Sezary's syndrome (55) is reported, including ultrastructural and immunohistochemical characterization of the cellular infiltrates.Atypical lymphocytes in the skin were evaluated at stages of both clinical exacerbation and improvement. During both stages, skin specimens revealed essentially similar findings. They were diffusely infiltrated by atypical lymphocytes with a characteristic nuclear convolution. The infiltrating cells exhibited T-cell markers which cross-reacted with the T -cells of the lymph nodes. Atypical convoluted cells in the peripheral blood were PA5 positive and peroxidase negative. The morphological and functional characteristics of the cellular infiltrates in 55 and its clinical independence from mycosisfungoides were discussed.