Paucity of intraepidermal FoxP3-positive T cells in cutaneous T-cell lymphoma in contrast with spongiotic and lichenoid dermatitis.
BACKGROUND
FoxP3 is the most specific available marker for regulatory T cells (Tregs). Tumor-associated FoxP3-positive Tregs have been identified in various neoplasms, including cutaneous T-cell lymphoma (CTCL). FoxP3 expression in CTCL varies across groups; few studies have compared CTCL with inflammatory conditions.


METHODS
Lesional skin biopsies from 20 patients with CTCL [13 mycosis fungoides (MF); 7 Sézary syndrome (SS)] and 22 with inflammatory dermatoses (11 spongiotic; 11 lichenoid or interface) were examined for FoxP3 expression by immunohistochemistry. Epidermal FoxP3-positive lymphocytes were counted as a percentage of the total epidermal CD3-positive T-cell population.


RESULTS
FoxP3-positive T cells composed the minority of infiltrate in all major categories. Lower numbers of epidermal FoxP3-positive T cells were observed in CTCL, particularly MF, than in inflammatory dermatoses (P < .001). CTCL neoplastic T cells did not express FoxP3.


CONCLUSIONS
FoxP3-positive T cells are less frequently encountered in MF than in inflammatory dermatoses. FoxP3-positive T cells occur in higher proportions in the dermis than in the epidermis and probably correlate with coexisting inflammatory components. CTCL neoplastic cells do not typically express a Treg phenotype and are associated with low numbers of FoxP3-positive Tregs in the infiltrate. FoxP3 expression by immunohistochemistry may aid histologic evaluation of these conditions.
Wada
David A
DA
Department of Dermatology, Mayo Clinic, Rochester, MN, USA.
Wilcox
Ryan A
RA
Weenig
Roger H
RH
Gibson
Lawrence E
LE
D002452:Cell Count; D003872:Dermatitis / Q000378:metabolism* / Q000473:pathology; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D017512:Lichenoid Eruptions / Q000378:metabolism* / Q000473:pathology; D009182:Mycosis Fungoides / Q000378:metabolism* / Q000473:pathology; D012751:Sezary Syndrome / Q000378:metabolism* / Q000473:pathology; D012867:Skin / Q000378:metabolism / Q000473:pathology; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology
C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors
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