Non-Melanoma Skin Cancers Coverage from Every Angle

Does PD-1 Expression Differ by Histology in Cutaneous Squamous Cell Carcinoma?

By: Celeste L. Dixon
Posted: Tuesday, June 4, 2019

In a letter to the editor of the British Journal of Dermatology, researchers described their investigation into the expression and localization of PD-1 and PD-L1 according to cutaneous squamous cell carcinoma differentiation using immunohistochemical staining. They found a significant difference in the proportion of PD-1 immunoreactivity based on the degree of cutaneous squamous cell carcinoma differentiation (P < .001). No prior work had examined the intrinsic expression of PD-1 in this type of skin cancer.

“We detected PD-1 expression in the membrane and cytoplasm of tumor cells of [cutaneous squamous cell carcinoma],” wrote corresponding author Young Min Park, MD, of the College of Medicine of Catholic University of Korea in Seoul, and colleagues. Specifically, using 29 biopsy specimens, moderate to strong PD-1 immunoreactivity was found in 100% of specimens of well-differentiated cutaneous squamous cell carcinoma, in 75% of moderately differentiated cutaneous squamous cell carcinoma, and in 10% of poorly differentiated cutaneous squamous cell carcinoma.

Given that “the proportion of PD-1 immunoreactivity was much higher in well-differentiated [cutaneous squamous cell carcinoma]…, it is reasonable to suggest that PD-1 may participate in the formation of well-differentiated [cutaneous squamous cell carcinoma],” wrote the team. “However, we could not find any significant difference in the proportion of PD-L1 immunoreactivity according to the degree of [cutaneous squamous cell carcinoma] differentiation.” Although PD-L1 expression has been reported as strongly associated with nodal metastasis of cutaneous squamous cell carcinoma, they noted, data from previous studies actually have conflicted over whether higher PD-L1 expression positively correlates with higher histologic grade of this type of skin cancer.

“Our results suggest that PD-1 can be a differential biologic marker of well-differentiated [cutaneous squamous cell carcinoma],” Dr. Park and co-investigators concluded.

Disclosure: The study authors’ disclosure information may be found at

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