High expression of CD56 (N‐CAM) in a patient with cutaneous CD4‐positive lymphoma

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Abstract
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‐β, γ, 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.