Immunologic studies documenting the development of mycosis fungoides following successful therapy of a large-cell lymphoma.

We describe a patient who developed mycosis fungoides, a T-cell neoplasm, two years following the chemotherapy and radiotherapy of a diffuse, large-cell ("histiocytic") lymphoma. Immunologic studies documented a "null-cell" phenotype for the large-cell lymphoma. Therefore, the proliferation of two distinct malignant lymphoid clones is believed to have developed in the patient. The value of immunologic marker studies in this case was to aid in the diagnosis of the two separate neoplasms, as well as to aid in the selection of appropriate specific therapy directed against each neoplasm. As the association of large-cell lymphoma and mycosis fungoides in one patient represents a very rare event, we discuss several hypotheses about the possible interrelation of the two neoplasms.