An ultrastructural study of cutaneous panniculitis-like T-cell lymphoma: cytoplasmic granules and active cellular and cell-to-matrix interaction mimic cytotoxic T-cells.

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare type of peripheral T-cell-derived lymphoma. A 30-year-old Japanese woman presented, complaining of skin lesions on her left hip. The cellular constituents in this SPTCL were of a mixed population. Not only tumor lymphoid cells, but also many macrophages, endothelial, fibroblasts, and fat cells were seen. The tumor cells immunostained positive for CD3 and CD8, but negative for CD4. Cytotoxic injury granule-related antigens of TIA-1 and granzyme B were positive in tumor cells. CD30. CD56, EBNA-2, LMP-1, CD20cy, and CD68 were all negative in the tumor cells. An ultrastructural study revealed that the lymphoma cells showed primitive cellular contacts with the neighboring tumor cells, interacted with the short villous dendrites of the opposing macrophage and fibroblast cellular membranes, and were associated with the vascular constituents, fat cells, and the extracellular matrix. Small aggregations of the granules were frequently seen in the cytoplasm. It was speculated that the tumor cells to some extent preserve the cytotoxic T-cell structure and function, have active cellular and cell-to-matrix interaction, contain characteristic cytoplasmic granules, and reveal unique histology like panniculities.