Dermatopathic lymphadenopathy. An immunophenotypic comparison of cases associated and unassociated with mycosis fungoides.

Documenting focal mycosis fungoides in lymph node biopsies that exhibit dermatopathic lymphadenopathy is morphologically difficult. Since mycosis fungoides is a lymphoma with the phenotype of mature T cells, usually of the T-helper class, the authors investigated whether there are alterations in the ratio of Leu 3a (T-helper):Leu 2a (T-suppressor) cells in dermatopathic lymphadenopathy in order to determine the significance of immunologic markers as a possible solution to the problem. Ten lymph node biopsy specimens with diagnostic evidence of dermatopathic lymphadenopathy, but not of mycosis fungoides, were studied with the use of fresh-frozen section immunohistochemistry (FS), cell suspensions (CS), or both; five of the specimens came from patients with known cutaneous mycosis fungoides, and the other five came from patients without mycosis fungoides. The mean Leu 3a/Leu 2a ratio was 7.0 +/- 1.06 (SE) in all 10 cases of dermatopathic lymphadenopathy studied by FS and 6.9 +/- 1.14 in the 6 cases studied by CS. These ratios were significantly higher (P less than 0.001) than the mean Leu 3a/Leu 2a ratios of 2.9 +/- 0.29 (FS) and 2.4 +/- 0.22 (CS) in control lymph nodes exhibiting nonspecific reactive follicular hyperplasia, but were comparable to the mean Leu 3a/Leu 2a ratio of 5.9 obtained in two lymph node biopsies with unequivocal involvement by mycosis fungoides. Despite the increase in Leu 3a staining cells in dermatopathic lymphadenopathy, however, there were no essential differences in the Leu 3a/Leu 2a ratios between patients with and those without known mycosis fungoides. The use of other antibodies reactive with T cells, such as anti-Leu 8, anti-Leu 9, and anti-Tac also did not aid in this discrimination. The results indicate that determination of the Leu 3a/Leu 2a ratio and use of other conventional T-cell monoclonal antibodies do not provide conclusive evidence in support of a presumptive or early diagnosis of mycosis fungoides in a lymph node which fails to show histologic evidence of the disease.