Diffuse large B cell lymphomas (DLBCL) is the largest group of NHLs, representing 49% of B cell cancers worldwide
[4]. The median age of prevalence is seventy years, although it has been diagnosed in young people and rarely in children, with a slight male prevalence
[5]. DLBCL is characterized by a high heterogeneity at both the clinical and biological levels because it arises from germinal center B cells at different stages of differentiation associated with recurrent genetic modifications which contribute to the molecular pathogenesis of the disease
[6]. On these bases, the DLBCL classification results are very complex and constantly evolving due to heterogenic variants in consideration to morphology, phenotype, genetic anomalies, prognosis and clinical features
[7]. DLBCL tumor mass may grow in lymph nodes and/or in other multiple external sites, but the gastrointestinal tract constitutes the most frequent primary tumor site
[8]. CD68
+ macrophages, tryptase
+ mast cells and microvascular density (MVD) have been evaluated in samples derived from DLBCL patients subdivided into two groups. The first group included patients who achieved a complete remission (responders), and the second included patients who never achieved a complete remission or incomplete remission after first-line chemotherapy, and who relapsed within six months (non-responders)
[9]. A higher number of both CD68
+ cells and microvessels in the non-responders group compared to the responders group has been observed
[9]. In DLBCL, a high expression of CD68
+ cells has been correlated with a poor prognosis
[10]. The higher percentage of tryptase
+ mast cells found in the non-responders’ group when compared with the responders’ group positively correlated with the MVD
[9], indicating the important role of mast cells in promoting and sustaining tumor angiogenesis in DLBCL. Bulky and residual tumors are considered to increase the risk of relapse in DLBCL patients
[11]. To investigate the complex relationships occurring between immune cells, stromal cells, endothelial cells and the tumor cells, the involvement of T cells in the control of bulky and non-bulky DLBCL development and their correlation with mast cells and MVD has been estimated
[12]. A significant reduction in CD3
+ cells in the TME of bulky compared to non-bulky disease has been reported, suggesting the loss of the immune control resulting in an increased cell proliferation, and consequently to a large tumor cell-mass in bulky DLBCL
[12].
Constitutively activated STAT3 is correlated with a more advanced clinical stage and overall poor survival rate of people with DLBCL
[13][14]. In addition, STAT3 is strongly activated in ABC-DLBCL and BCL6-negative normal germinal center B cells representing both the second oncogenic pathway in ABC-DLBCL and an additional therapeutic target for treatment
[15]. The DLBCL GCB and ABC subgroups of patients have been compared and by means of RNAscope technology a significantly higher number of STAT-3-expressing cells in ABC group as compared to GCB has been shown
[16]. Tumor vessels in ABC samples appeared lined by endothelial cells expressing both FVIII and STAT3 signals, while in GCB samples, only few vessels co-expressed FVIII and STAT3
[16]. A higher Ki67 expression in tumor cells and a higher number of CD163
+ macrophages in ABC patients as compared with GBC ones has been observed, together with a high density of CD3
+ and CD8
+ cells, which correlated with STAT3 expression and microvascular density
[17]. In the DLBCL TME, the prognostic value of the CD4/CD8 ratio has been associated with both better and worse survival in different studies
[18]. No variation in CD4
+ cells in ABC with respect to GCB has been observed but a higher CD8
+ cell infiltrate in the ABC group associated with a decreased CD4/CD8 ratio
[17]. In addition, a higher STAT3 expression is associated not only with CD8
+ cells but also with a higher M2 TAM cell infiltration
[17].