Jd. Nuckols et al., Quantitation of intraepidermal T-cell subsets in formalin-fixed, paraffin-embedded tissue helps in the diagnosis of mycosis fungoides, J CUT PATH, 26(4), 1999, pp. 169-175
Differentiation between mycosis fungoides (MF) and cutaneous inflammatory p
rocesses can usually be made on clinical and histologic grounds. In difficu
lt cases, immunohistochemical studies can be helpful since MF infiltrates u
sually contain a predominance of CD4+ lymphocytes, while most inflammatory
lesions usually have a mixture of CD4+ and CD8+ lymphocytes. However, this
determination has traditionally required the use of frozen tissue, thus sev
erely limiting its usefulness. Recently, antibodies that differentially lab
el CD LS and CD8+ lymphocytes in formalin-fixed, paraffin-embedded tissue h
ave become available (OPD4 and C8/144B respectively, DAKO (Carpinteria, CX,
USA). This study tests the utility of these antibodies in the pathologic d
iagnosis of MF and inflammatory lesions with significant exocytosis, In 9 c
ases of MF for which both frozen and fixed tissues were available for compa
rison, the OPD4+ cell count in fu;ed tissue was significantly lower than th
e Leu-3a+ cell count in frozen tissue, Also, the C8/144B+ cell count in fix
ed tissue was higher than the Leu-2a+ cell count in frozen tissue, although
this difference was not significant statistically. In a larger series for
which only fixed tissue was available, epidermal CD4:CD8 ratios were signif
icantly greater in 23 MF cases (mean 4.0+/-4.76) than in 35 inflammatory ca
ses (mean 0.6+/-0.42; p=0.001). Thus, although the studied antibodies appea
r to detect different epitopes in frozen versus paraffin-embedded tissue, d
emonstration of an elevated CD4:CD8 ratio in fixed tissue supports the diag
nosis of MF, and is a helpful adjunct to routine histopathology.