Mesotheliomas show higher hyaluronan positivity around tumor cells than metastatic pulmonary adenocarcinomas.

Hyaluronan is a unique glycosaminoglycan of the extracellular matrix, abundant in normal connective tissues but highly increased in many pathological conditions like cancer. Mesothelioma, one of the most malignant cancer types, is associated with high content of hyaluronan, with elevated levels of hyaluronan in pleural effusions and serum of the patients. Metastatic lung adenocarcinomas are typically less aggressive and have a better prognosis as compared to mesotheliomas, a reason why it is highly important to find reliable tools to differentiate these cancer types. The main purpose of this study was to evaluate the amount of hyaluronan, hyaluronan producing synthases (HAS's) and hyaluronan receptor CD44, in mesothelioma and metastatic lung adenocarcinomas. Furthermore, we wanted to clarify the role of hyaluronan, CD44 and HAS's as putative markers for differentiating malignant mesothelioma from metastatic lung adenocarcinomas. The main finding of this study was that mesotheliomas are significantly more positive for hyaluronan staining than metastatic adenocarcinomas. Unexceptionally, a trend of CD44 positivity of stromal cells was higher in adenocarcinomas as compared to mesotheliomas. However, no statistically significant differences were found between the staining of any of the HAS isoenzymes either in tumor cells or stromal cells of different groups of cases. The results show that there are significant differences in hyaluronan content between metastatic lung adenocarcinomas and mesotheliomas. However, as previous studies have suggested, hyaluronan alone is not a sufficient independent marker for diagnostic differentiation of these cancer types, but could be utilized as a combination together with other specific markers.