These cells occasionally displayed a stellate-shaped or fusiform architecture with cytoplasmic projections, thereby assuming a mesenchymal appearance (Fig. 3a). In these areas, some of the carcinoma cells—especially those presenting morphological alterations—co-expressed epithelial membrane antigen and α-smooth muscle actin. The former stain had a purple membranous or cytoplasmic appearance and the latter stain was brown and cytoplasmic (Fig. 3a and b). Fig. 3 a Small islands of carcinoma cells at the invading front showing a stellate-shaped and fusiform architecture with cytoplasmic projections, some with a fibroblastoid appearance.

Remnants of epithelial membrane antigen staining (purple membranous/cytoplasmic stain) disclose their epithelial origin. Brownish cytoplasmic staining of α-smooth muscle actin is observed in a few foci within the carcinoma cells (arrows) (anti-epithelial buy CA4P membrane antigen and anti-α-smooth muscle actin antigen antibodies, Fast-red and 3,3′-diaminobenzidine (DAB) double immunostaining; bar 50 μ). b Spindle carcinoma cells with remnants of epithelial membrane antigen staining and check details an area of brown cytoplasmic stain compatible with α-smooth

muscle actin positivity (thin arrow). A cluster of carcinoma cells negative for epithelial membrane antigen and very positive for α-smooth muscle actin is seen in the upper left corner (thick arrow) (bar 20 μ) The higher the SMF counts, the more frequent the “network” distribution of the SMF tended to be, and the more frequent the presence of carcinoma cells

co-expressing epithelial membrane antigen and α-smooth muscle actin (Table 2). Discussion The results of our study showed that presence of SMF was associated with carcinoma of the tongue, while these cells were sparse to absent in pre-malignant lesions. In addition, we found that tumors were heterogeneous in the extent of SMF and their pattern of distribution and morphological features. Indications of an association between squamous cell carcinoma and SMF were reported in previous studies that employed cell lines [25] and specimens of squamous cell carcinoma of the entire oral cavity [26, 27]. The presence of SMF was recently analyzed in a series of tongue carcinomas versus normal and dysplastic epithelial lesions from the entire oral mucosa [28]. In that study, in which frequency of SMF was assessed by a vague semi-quantitative scale, it was reported that SMF were found exclusively in carcinoma (~60%) and not in any of the dysplastic lesions. In contrast, in the present study, tongue carcinomas were analyzed versus tongue dysplastic lesions and the frequency of SMF was assessed by a systematic immunomorphometric S63845 method.