KRT17 and sarcomatoid carcinoma: They exhibit a fast growth leading to poorly differentiated squamous cell carcinomas (Fig. 1b), which rapidly progress, lose the expression of differentiation markers such as K10, K6 and K17 [15], and become highly undifferentiated carcinomas (Fig. 1c) and in, some cases evolve to spindle cell carcinomas (Fig. 1d), possibly by means of a premature EMT process.