Heterogeneity of PD-L1 expression and CD8 tumor-infiltrating lymphocytes among subtypes of cutaneous adnexal carcinomas.

Background: Adnexal carcinomas are rare and heterogeneous skin tumors, for which no standard treatments exist for locally advanced or metastatic tumors.

Aim Of The Study: To evaluate the expression of PD-L1 and CD8 in adnexal carcinomas, and to study the association between PD-L1 expression, intra-tumoral T cell CD8 infiltrate, and metastatic evolution.

Materials And Methods: Eighty-three adnexal carcinomas were included. Immunohistochemistry using anti-PD-L1 monoclonal antibodies (E1L3N and 22C3) and CD8 was performed. PD-L1 expression in tumor and immune cells, and CD8 tumor-infiltrating lymphocyte (TIL) density were analyzed semi-quantitatively.

Results: Among the 60 sweat gland, 18 sebaceous and 5 trichoblastic carcinomas, 11% expressed PD-L1 in ≥ 1% tumor cells, more frequently sweat gland carcinomas (13%, 8/60) including apocrine carcinoma (40%, 2/5) and invasive extramammary Paget disease (57%, 4/7). Immune cells expressed significantly more PD-L1 than tumor cells (p < 0.01). Dense CD8 TILs were present in 60% trichoblastic, 43% sweat gland, and 39% sebaceous carcinomas. CD8 TILs were associated with PD-L1 expression by tumor cells (p < 0.01). Thirteen patients out of 47 developed metastases (27%) with a median follow-up of 30.5 months (range 7-36). Expression of PD-L1 by tumor cells was associated with the development of metastasis in univariate analysis (HR 4.0, 95% CI 1.1-15, p = 0.0377) but not in multivariate analysis (HR 4.1, 95% CI 0.6-29, p = 0.15).

Conclusion: PD-L1 expression is highly heterogeneous among adnexal carcinoma subtypes, higher in apocrine carcinoma and invasive extramammary Paget disease, and associated with CD8 TILs. Our data suggest the interest of evaluating anti-PD1 immunotherapy in advanced or metastatic cutaneous adnexal carcinoma.