Abstract

T-cell prolymphocytic leukemia (T-PLL) is a rare T-cell malignancy that typically demonstrates an aggressive course, with cutaneous involvement reported in approximately 25% of cases. Cutaneous involvement may be associated with poorer prognosis. The typical immune phenotype is of mature T cells, with negative expression of terminal deoxynucleotidyl transferase (TdT). Variability in CD4 and CD8 expression is observed between cases, with most cases being CD4⁺ and CD8^-. CD4⁺/CD8⁺ and CD4^-/CD8⁺ phenotypes are uncommon, representing approximately 25% and 15% of cases, respectively. A retrospective chart review identified five cases of cutaneous T-PLL diagnosed at our institution between January 2006 and August 2024. Four cases had a known history of T-PLL prior to the appearance of cutaneous involvement, while one patient had a nonspecific rash at the time of initial diagnosis of T-PLL, and underwent biopsy demonstrating cutaneous T-PLL several months later after the rash failed to resolve. In our cohort, one case demonstrated a CD4⁺/CD8^- phenotype, three cases were CD4⁺/CD8⁺, and one case was CD4^-/CD8⁺. All CD8⁺ cases demonstrated angiocentricity, with angiodestruction seen in three out of four CD8⁺ cases. These features were not observed in the CD4⁺/CD8^- case. Literature review of cases of cutaneous T-PLL found that of cases that noted the presence of angiocentricity and vasculitis, many demonstrated a CD4⁺/CD8⁺ or CD4^-/CD8⁺ phenotype. We hypothesize that CD8⁺ T cells with a cytotoxic phenotype could predispose towards angiocentricity and angiodestruction in cases of T-PLL that demonstrate expression of CD8.