Microlocalization of CD68+ tumor-associated macrophages in tumor stroma correlated with poor clinical outcomes in oral squamous cell carcinoma patients

CD68 has been widely used as a pan-macrophage marker for tumor-associated macrophages (TAM) which always involve in carcinogenesis. But the correlations between CD68(+) TAMs and prognosis of patients show to be inconsistent, which might due to lack of specific markers of TAMs. We here found that the microlocalization of CD68(+) TAMs also played a unique role in prognosis of patients with oral squamous cell carcinoma (OSCC). CD68(+) TAMs were identified in paraffin-embedded OSCC specimens (n=91) by using immunohistochemistry. The number of CD68(+) TAMs was remarkably increased from adjacent none-neoplasia tissues (NT) to tumor nest (TN), but tumor stroma (TS) was infiltrated with highest frequency of CD68(+) TAMs (P<0.0001). Unexpectedly, more CD68(+) TAMs in TS, but not NT or TN, were associated with high tumor grade (P=0.033), lymph node metastasis (P=0.034), and shorter 10-year overall survival time, disease free survival. Considering TAMs was derived from monocytes in peripheral blood, we assessed the relationship between leukocytes in peripheral blood and CD68(+) TAMs in OSCC and found that more CD68(+) TAMs in TS were accompanied with decreased monocytes and lymphocytes in peripheral blood (P<0.05). Although Cox regression analysis revealed that CD68(+) TAMs in TS were not an independent prognostic factor for OSCC patients, we raised a possibility that the microlocalization of CD68(+) TAMs was an indispensable factor for the advance of OSCC.