Ultrastructural features of mycosis fungoides.

Abstract

The ultrastructural features of lymphocytes, polymorphonuclear leukocytes, plasma, reticulum, and so-called mycosis cells were similar in the cutaneous infiltrates from patients with the plaque, tumor, eczematous or premycotic, poikilodermic, and erythrodermic forms of mycosis fungoides. The distinction of mycosis cells from reticulum cells appears to depend upon the greater degree of nuclear irregularity and lobulation in the former cell type. The lack of more objective, qualitative differences between the two suggests that the mycosis cell represents a histologic variant of the reticulum cell. The diagnostic specificity of the mycosis cell is limited, since cells with comparable ultrastructural features were encountered, albeit rarely, in biopsies of two of five patients with such banal dermatoses as chronic nonspecific dermatitis and psoriasis. No electron microscopic information which might affirm or deny the specificity of mycosis fungoides as a clinicopathologic entity was evident from this study. Although reticulum cells in lesions of mycosis fungoides were similar to those encountered in nodal examples of reticulum cell sarcoma, mycosis cells were dissimilar from Reed-Sternberg cells encountered in nodal Hodgkin’s disease. The latter cells were considerably larger and possessed more prominent nucleoli than were observed in mycosis cells. Intranuclear inclusions were noted in reticulum and mycosis cells in the lesions of mycosis fungoides, nonneoplastic dermatoses, nodal Hodgkin’s disease, reticulum cell sarcoma, and occasional normal epidermal and endothelial cells. At least some of these bodies in the patients with mycosis fungoides are artifactual, representing entrapped cytoplasmic material. It is concluded that the diagnosis of mycosis fungoides can be made more assuredly on the basis of its histopathologic rather than ultrastructural features.