Appendix tumor microenvironment

The pathological features of the appendix tumors fundamentally recall those of the more frequent colorectal neoplasms, although with a higher relative incidence of carcinoids, due to the abundant presence of enteroendocrine cells in the appendix wall. Moreover, different types of lymphomas, Hodgkin and non- Hodgkin, arising from the extra-nodal mucosal- associated lymphatic tissue, can be encountered. The appendix tumor microenvi ronment (TME) consists of a cellular compo nent and of a noncellular component: the former includes the immunocompetent cells, while the latter represents the support stroma. Particularly in carcinoids, the immune cell reaction can be explicated by tumor- infiltrating lymphocytes, which, in some circumstances, may arrange around and inside the tumor in a brisk fashion influencing favorably the prog nosis. This active reaction has to be distin guished from any preexisting inflammatory condition of the appendix and from superimposed posed tumor complications, such as infection or ischemia. In practice, we consider the appendix TME a complex framework with immunological, mechanic, and metabolic functions, all supported by a marked neo-lymphoangiogenesis.