The lymph node in mycosis fungoides: a light and electron microscopy and immunohistological study supporting the Langerhans' cell-retrovirus hypothesis.

This paper describes the light and electron microscopy and monoclonal antibody findings in the lymph nodes of nine patients with mycosis fungoides. Four cases showed dermatopathic change characterized by close association between small convoluted T4 lymphocytes and T6 antigen-presenting cells (Langerhans' and indeterminate dendritic cells) in the sinuses and paracortical zones. The T4:T8 ratio was between 3 and 5:1. One case showed dermatopathic change but included large convoluted T4 lymphocytes and occasional T10 lymphocytes. The T4:T8 ratio was 4:1. The antigen-presenting cells were mostly T6 negative (interdigitating reticulum cells). One case showed extensive paracortical expansion by small and large convoluted T4 lymphocytes. The T4:T8 ratio was 20:1. Few B lymphocytes and antigen-presenting cells were present. Two cases showed partial and one case total effacement by atypical lymphoid tissue. This included small and large convoluted T4 lymphocytes and T4 immunoblasts. The T4:T8 ratios were between 30 and 40:1. The changes in their antigen-presenting cell population were complex. Langerhans' cells in one case generally failed to express T6 antigen and in two displayed histiocyte features. In one case, both immature and budding type C retrovirus-like particles were identified in Langerhans cells. One extracellular mature type C virus-like particle was identified in another case. No ultrastructural distinction could be made between similarly sized primary lysosomes and possible intracytoplasmic mature type C retrovirus particles. These findings support the hypothesis that mycosis fungoides may represent an altered dermatonodal cycle resulting from an interaction between retrovirus, Langerhans' cells and lymphocytes.