Usefulness (or Lack Thereof) of Immunophenotyping in Atypical Cutaneous T-Cell Infiltrates

Abstract

Our purpose was to evaluate the interobserver concordance for the diagnoses of mycosis fungoides (MF), atypical dermatoses (AD), and benign dermatoses (BD) and the impact of T-cell immunophenotyping on the diagnoses MF, AD, and BD. Specimens of MF (n = 57), AD (n = 27), BD and normal skin (n = 54) were reviewed by 2 hematopathologists and 1 dermatopathologist to establish diagnostic interobserver concordance by routine morphologic examination. Immunophenotyping was performed to evaluate expression of CD2, CD3, CD4, CD5, CD7, CD8, CD20, CD30, and MIB-1. The interobserver concordance was fair to moderate compared with the original diagnosis. Partial deletion of CD2 alone was associated significantly with MF. Epidermal deletions of 2 or 3 T-cell antigens or 2 T-cell antigens not including CD7 were associated significantly with MF. An elevated CD4/CD8 ratio correlated with MF. Morphologic features were most diagnostic of MF. Immunophenotyping generally resulted in downgrading of the reaction pattern but was helpful in distinguishing MF from benign dermatoses.

Diagnosis of mycosis fungoides with different algorithmic approaches

“…29,30 IHC studies typically look for the loss of T-cell antigens in epidermal lymphocytes as a finding associated with MF, with the important caveat that the loss of CD7 in epidermal lymphocytes has been observed in MF and inflammatory dermatoses to varying degrees, and by itself is generally not specific. 9 Decreased expression of CD2 or CD5 has been described as very specific, but relatively insensitive, for MF, a conclusion supported by our study results. 9,19,27 IHC assessment of the CD4/CD8 ratio has also been used in the evaluation of MF, and in general has been reported to have low sensitivity and high specificity; however, the cutoff value used varies between different studies.…”

“…9 Decreased expression of CD2 or CD5 has been described as very specific, but relatively insensitive, for MF, a conclusion supported by our study results. 9,19,27 IHC assessment of the CD4/CD8 ratio has also been used in the evaluation of MF, and in general has been reported to have low sensitivity and high specificity; however, the cutoff value used varies between different studies. 9,11,20 Though evaluation of the CD4/CD8 ratio is a common starting point, based on our findings only a complete evaluation of all T-cell antigens is probably of substantial utility, but even then will have limited sensitivity.…”

“…9,19,27 IHC assessment of the CD4/CD8 ratio has also been used in the evaluation of MF, and in general has been reported to have low sensitivity and high specificity; however, the cutoff value used varies between different studies. 9,11,20 Though evaluation of the CD4/CD8 ratio is a common starting point, based on our findings only a complete evaluation of all T-cell antigens is probably of substantial utility, but even then will have limited sensitivity. Combining IHC findings and clonality may be useful, especially in cases where only CD7 is lost, since concurrent clonality resulted in high specificity for a diagnosis of MF.…”

Expression of programmed death‐1 in skin biopsies of benign inflammatory vs. lymphomatous erythroderma

“…Loss of CD7 is a common feature in CTCL, but has also been reported in a variety of benign inflammatory dermatoses, probably as a result of chronic T-cell activation. 15,16 Unlike loss of other T-cell antigens, such as CD2, CD3 and CD5, loss of CD7 is therefore not considered as a useful criterion to differentiate between CTCL and inflammatory skin diseases. 15,16 In the present study, loss of CD7 by > 50% of the infiltrating T cells was observed in 16 of 24 (67%) cases of SS, and only in four of 30 (13%) cases of EID.…”

Combined Use of PCR-Based TCRG and TCRB Clonality Tests on Paraffin-Embedded Skin Tissue in the Differential Diagnosis of Mycosis Fungoides and Inflammatory Dermatoses

“…Mycosis fungoides (MF) is the principle form of cutaneous T-cell lymphoma and accounts for nearly 50% of all primary cutaneous lymphomas. 1 In a proportion of cases, especially during the early stages, it is difficult to distinguish MF from some reactive inflammatory dermatoses (ID) clinically and histopathologically, and thus a definitive diagnosis is often preceded by a variably long period. Based on the fact that the tumor cells of lymphomas harbor identically (clonally) rearranged T-cell receptor genes whereas reactive skin disorders consist of cells with polyclonal T-cell receptor genes, 2 T-cell receptor clonality testing is commonly performed on cases of suspected MF as an ancillary study to provide additional evidence for diagnosis.…”