Absolute monocyte count has a diagnostic role in distinguishing tumor marker-negative TGCT from benign testicular tumor via CCL2 regulation

Clinically, for testicular tumor patients with negative tumor markers, how to distinguish the malignant from the benign is a difficult problem. This study aimed to assess the clinical significance of the absolute monocyte count (AMC) in differential diagnosis of testicular germ cell tumor with stage S0 (TGCT(S0)) and benign testicular tumor. In this retrospective single-center study, a total of 90 patients newly diagnosed with benign testicular tumor or TGCT(S0) were reviewed. All patients received surgical intervention as the primary treatment method. AMC and other clinicopathological parameters were analyzed. Receiver operating characteristic (ROC) curves were constructed to assess the diagnostic power of investigated parameters, and to determine the optimal cutoff values. Kaplan–Meier curve analysis was used to study the survival of patients with TGCT(S0). qRT-PCR and immunohistochemistry (IHC) were performed to examine the expression of C-C motif chemokine ligand 2 (CCL2) mRNA and protein respectively. Differential gene expression and functional enrichment analysis were performed using Gene Expression Omnibus and the Cancer Genome Atlas databases. The mean preoperative AMC in patients with TGCT(S0) was significantly higher than that in patients with benign testicular tumor (P = .020). AMC > 0.485*10^9/L was identified to be associated with the presence of TGCT(S0) (hazard ratio [HR] = 3.074, P = .026), and patients with higher AMC level had worse progression free survival (PFS) (P = .047). Furthermore, AMC combined with lactate dehydrogenase (LDH) achieved a better diagnostic efficacy for TGCT(S0) (area under curve [AUC] = 0.695). Tumor-associated macrophages (TAMs) signature gene CCL2 was highly expressed in TGCT compared with normal testicular tissue. Functional enrichment analysis showed that CCL2 is closely involved in the Extracellular Matrix Organization pathway and positively correlated with the expression of various matrix metalloproteinases (MMPs). Elevated AMC may serve as a predictor of higher risk of TGCT(S0), and CCL2 mediated TAMs infiltration and MMPs secretion is essential for the tumorigenesis of TGCT.