The intracutaneous growth of murine lymphomas: epidermal invasion is characteristic of multiple tumor phenotypes.

Affinity of lymphoid cells for the epidermis (epidermotropism) is characteristic of the cutaneous T-cell lymphomas, mycosis fungoides and the Sézary syndrome. Consistent with numerous studies indicating that mycosis fungoides is a neoplasm of OKT4+T8- ("helper/inducer") T lymphocytes is the possibility that epidermotropism is a phenotypic hallmark of this subset of malignant T cells. This proposal was investigated in mice using 8 phenotypically characterized lymphomas of BALB/c origin: 3 histiocytic (phagocytic, lysozyme-positive, FcR+, Ig-, Thy 1-), 1 B-cell (IgM+, FcR+, Thy 1-), and 4 T-cell (Ig-, Thy 1+) lines, including 1 with markers of mouse helper/inducer T cells (Lyt1+23-), 2 with suppressor/cytotoxic markers (Lyt1-23+), and 1 with markers of immature thymocytes (Lyt1+23+). The intracutaneous growth pattern of these lines was studied on hematoxylin and eosin-stained sections through the centers of tumors obtained at times after intradermal injection into parallel groups of syngeneic mice. All of these lymphomas manifested variable epidermotropism that followed a typical sequence. Following dermal growth and spread to the dermal-epidermal junction, tumor cells appeared within the stratum spinosum. Subsequently, collections of cells appeared in spaces within the epidermis (Pautrier-like microabscesses) in tumors greater than 2 cm in diameter, coincident with early epidermal necrosis. Thus, in this animal model it is clear that the intraepidermal invasion/growth does not correlate with the helper/inducer T-cell surface phenotype. These observations are nonetheless consistent with recent studies using monoclonal antibodies to cell surface antigens which have demonstrated a heterogeneity of lymphoid cell subsets within the epidermis in lesions of mycosis fungoides and of other malignant and benign dermatoses.