S100A4 and malignant mesothelioma: Interestingly, our results obtained on experimental cell lines and tumor models of sarcomatoid MM in rats corroborated the work of Fassina et al. on a collection of 109 malignant mesothelioma specimens from patients who observed a progressive increase in S100A4 immunohistochemical staining from epithelioid to biphasic and sarcomatoid subtypes [33].