Although we investigated a relatively small number of tumors, not all the examined cases presented a homogeneous pattern of SMF. The proportion between an existing malignancy and SMF ranged from tumors in which the SMF were incidental to tumors in which they predominated. Furthermore, the layout of the SMF around Selleck ML323 the tumor islands generated different patterns, such that tumors with fewer SMF usually displayed spindle, delicate SMF organized in bundles that subtly surrounded the carcinoma at its periphery, while tumors with an abundance of SMF often featured epithelioid SMF that amalgamated

with the carcinoma cells and were organized in a syncytium-like, cellular network. These differences might have an impact on defining the biological aggressiveness of the tumors, based on the fact that the SMF are considered as the biological “factories” for a vast range of mediators that back up, enhance and

promote tumor’s invasion. These mesenchymal cells are major suppliers of matrix metalloproteinases, whose function has been recently extended and consists not only of degradation of extra-cellular matrix proteins but also of an active part in tumor initiation, growth, migration, invasion, formation of metastasis, angiogenesis and selection of apoptosis-resistant clones [29]. An association between metalloproteinases and a more aggressive biological behavior of oral squamous cell carcinoma and a poorer prognosis has been reported stiripentol [30, 31]. We also observed a trend wherein the more frequent the expression of cancer-derived transforming growth factor-β, the more abundant were the SMF in the adjacent 17DMAG mw tumor. This is in accordance with the recognized key role of this growth factor in the transformation of resident fibroblasts into myofibroblasts [9, 10]. In addition, it is known that transforming

growth factor-β plays a crucial role, together with other factors, in another biological process—epithelial-mesenchymal transition, which has been described as a physiological process during normal embryogenesis on the one hand, and in pathological conditions, such as fibrosis and cancer, on the other hand [12, 13, 32]. In the present study, some of the SMF had an epithelioid appearance at the tumor-connective tissue interface, while some of the carcinoma cells demonstrated a spindle, fibroblastoid appearance due to a nearly total loss of cohesion with their neighboring cells. These morphological features highlighted the blurred boundary between the epithelial and mesenchymal phenotypes. In addition, double immunoreactivity revealed that malignant cells were more commonly found in tumors that displayed high numbers of SMF with a “network” pattern of distribution. It seems that under certain conditions determined by the tumor needs, the reservoir of SMF (mostly of resident fibroblast origin) is probably enriched by carcinoma cells that could undergo epithelial-mesenchymal transition [12, 13, 32, 33].

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