Cutaneous lymphoma is a disease characterized with massive skin infiltration of lymphoid malignant cells. They commonly express some T-cell markers, such as CD2, CD3, CD4, and CD7, and thus termed as CTCL (cutaneous T cell lymphoma). Here, we present a case with CD56/N-CAM-positive cutaneous lymphoma, which appears lymphocytic morphology and expresses CD4, but does not express CD2, CD3, CD8, CD14, CD16, CD57, and CD20. The most malignant cells contained no distinctive azurophilic granules in the cytoplasm. Southern blot analysis revealed that T cell receptor-beta, gamma, and immunoglobulin heavy chain genes in the cells were in germ-line configurations. Electron microscopic examination showed characteristics of lymphoid cells with higher nucleocytoplasmic ratio and lacked structures typical of other cell types (i.e., epithelial cells, neuroendocrine cells, and mesenchymal cells). Thus, the cells are likely to be immature lymphoid cells. Histological analysis revealed the cells infiltrate mainly into the dermis with angiocentric growth pattern. The clinical course was aggressive, with rapid involvement of bone marrow and central nervous system. These striking features of the patient may represent a novel fraction (CD2-, CD4+, and CD56+) of cutaneous lymphoma.

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Vesiculo-globular bodies, 40 nm in diameter, are present in melanosomes. The mode of their involvement in melanosomal differentiation was studied by ultrastructural comparison of eu- and pheomelanogenesis occurring in retinal and follicular melanocytes. We found that the number and distribution of these bodies differ significantly with types of melanogenesis and tissues. They were not affected by physical stimuli nor by embryonic origin of melanocytes. The earliest form of melanosomes is identical in eu- and pheomelanogenesis. The vesiculo-globular bodies are involved in organization of melanosomal constituents. In eumelanogenesis, they are more numerous in feather than in retina and hair. They are least numerous in white hair and pink eyes where melanization is blocked. During melanosomal development, they become associated with melanosomal inner lamellae and their outer surface becomes melanized, but their core is hardly melanized, thus leaving small vesicular structures. In pheomelanogenesis, their number is almost equal in feather and hair. Lamellae are not formed, but these bodies fuse with each other to form an amorphous matrix on complete differentiation of melanosomes.

Fast antigen is a cell surface protein that mediates apoptosis. Using immunohistological, flow cytometry and electron microscopic analyses, we investigated the expression of Fas antigen on various skin tissues, and on cultured SV40-transformed human epidermal keratinocyte cell line KJD and human skin squamous cell carcinoma cell line HSC. The Fas antigen was widely distributed in skin components such as the keratinocytes in the lower portion of the epidermis, epidermal dendritic cells, endothelial cells, fibroblasts, apocrine glands, eccrine sweat glands, sebaceous glands, some normal melanocytes and infiltrating lymphoid cells. It was also strongly expressed on the keratinocytes of lichenoid eruptions seen in lupus erythematosus and lichen planus, and on the spongiotic or acanthotic epidermis seen in chronic eczema, adult T-cell leukaemia/lymphoma (ATLL) and atopic dermatitis. Its expression was closely correlated with lymphoid infiltrating cells and it was strongly expressed in lymphoid neoplastic cells, particularly ATLL cells, and fibroblasts seen in dermatofibroma. However, the antigen was not detected on basal cell epithelioma cells, some malignant melanomas or any junctional naevi. The cell lines KJD and HSC strongly expressed the Fas antigen, and crosslinking of the Fas antigen by an anti-Fas monoclonal antibody induced apoptosis of these cell lines. These results indicate that the apoptosis-mediating Fas antigen may play an important role in normal skin turnover and cell differentiation, in immune regulation of skin tumours, and in the pathogenesis of various skin diseases.

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