Trypanosoma (subgenus Megatrypanum) theileri was first identified over one hundred years ago, and is a widespread parasite in cattle. Its life cycle within the mammalian host has rarely been reported. Whether there is an intracellular stage in tissues is unknown and such a stage has not been demonstrated experimentally. Intriguingly, using Giemsa staining with light microscopy and transmission electron microscopy examination, we found that the parasite was able not only to attach to cells but also to invade several phagocytic and non-phagocytic mammalian cells. Based on these findings, we conducted further investigations using a special antibody in immunofluorescence confocal images. Moreover, we examined a series of possible events of cell invasion in T. theileri. The results revealed that GM1, a marker of membrane rafts, was implicated in the mechanism of entry by this parasite. After incubation with tissue culture trypomastigotes, the gelatinolytic activity was significantly increased and accumulated at the attachment sites. Using ultrastructural localization detection by CytoTracker live imaging and confocal immunofluorescence microscopy, we found that lysosome fusion and the autophagy pathway were engaged in invaginating processes. T. theileri amastigotes also invaded cells and were enclosed by the lysosomes. Furthermore, tissue-cultured trypomastigotes were found to be capable of triggering intracellular free Ca(2+) transients and TGF-β-signaling. Our findings that intracellular amastigote stages exist in mammalian cells infected with T. theileri and that the invasion processes involved various host cell components and cell signalings were extremely surprising and warrant further investigation.

Background The prognostic relevance of extranodal extension (ENE) for salivary gland carcinoma (SGC) remains unclear. The present study is undertaken to investigate the predictive significance of pathological nodal parameters in surgically treated patients with nodal metastatic SGC. Methods This multicenter cohort included 114 patients with pathologically proven node‐positive SGC between 2000 and 2014. Possible correlations of clinicopathological parameters and outcomes were examined. Results The median follow‐up was 69 months (range, 11‐173 months). The multivariate analysis identified metastatic node number (1‐2 vs 3‐6; 1‐2 vs ≥7) as an independent predictor for regional control (P = 0.005; P = 0.02), locoregional control (P = 0.008; P = 0.04), distant metastasis‐free survival (P = 0.17; P = 0.006), disease‐free survival (P = 0.05; P = 0.002), and overall survival (P = 0.18; P = 0.009), whereas ENE was not associated with survival outcomes. Conclusions Metastatic node number, not ENE, is an independent node‐related prognosticator for SGC. Integration of ENE into the American Joint Committee on Cancer 8th edition staging criteria may not improve prognostic performance.