Intimal sarcomas are rare, aggressive neoplasms that arise from large blood vessels. Characterization of the tumor immune microenvironment may suggest new treatment strategies.
Seventeen specimens from 7 patients were labeled by immunohistochemistry for programmed cell death 1 ligand 1 (PD-L1), CD45, CD8, CD4, FOXP3, CD20, CD68, and LAG3. The immune cell density was scored as a percentage of the tumor area (1+ [50%]); PD-L1 expression was scored on tumor cells and on intratumoral immune cells. Immune marker density was quantified using image analysis software.
All intimal sarcomas showed immune cell infiltration (41% were 1+, 53% were 2+, 6% were 3+). Tumor and immune cell PD-L1 labeling was seen in 35% and 76% of cases, respectively; PD-L1+ intimal sarcomas had higher CD45+, CD8+, FOXP3+, CD68+, and leukocyte activation gene 3 (LAG3)+ cell densities (P ≤ .01). Similarly, PD-L1 expression on immune cells correlated with higher densities of CD8+ and FOXP3+ cells (P < .04). Higher LAG3+ cell density correlated with higher CD68+ cell density and necrosis (P < .05). One patient with prolonged survival had the highest immune cell density and PD-L1 expression.
These data show that intimal sarcomas have an active tumor microenvironment with an adaptive pattern of PD-L1 expression. Our results suggest that immunotherapy may be an effective treatment option.

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