Prognostic significance of tumor immunity in surgically resected pulmonary pleomorphic carcinoma

Background: Pulmonary pleomorphic carcinoma (PPC) is a rare aggressive neoplasm, with dismal prognosis. Whether tumor immunity is associated with the progressive biological behavior of PPC remains unclear. The purpose of this study was to examine the prognostic significance of tumor immunity-related markers such as programmed death-1 ligand (PD-L1) and CD4⁺ or CD8⁺ tumor-infiltrating lymphocytes (TILs) in patients with surgically resected PPC. Patients and Methods: Ninety-nine patients with surgically resected PPC were assessed by immunohistochemistry. The expression of PDL1, CD4, and CD8 was examined in specimens of the resected tumors. Results: PD-L1 was highly expressed in 61% (60/99) of lesions and high expression of CD4 and CD8 was identified in 42% (42/99) and 51% (51/99) of lesions, respectively. There was no relationship between the expression PD-L1 and the numbers of CD4⁺ or CD8⁺ TILs. The expression of PD-L1 was not identified as a significant prognostic marker; however, a low number of CD4⁺ TILs was identified as an independent marker for predicting a worse outcome after surgical resection of PPC, especially in patients with an epithelial component of adenocarcinoma or early stage of disease. By univariate analysis, a low number of CD8⁺ TILs was found to be a significant prognostic marker linked to poor overall survival in patients with non-adenocarcinoma components. Conclusion: A low number of CD4⁺ TILs is an independent marker for predicting a favorable prognosis after surgical resection in patients with PPC, especially in patients with adenocarcinoma components or early stage of disease.