NTRK2 and skin squamous cell carcinoma: In particular, TrkA (NTRK1) and TrkB (NTRK2) receptor mRNAs are markedly expressed in MD/PD cSCC, while CD271 mRNA (NGFR) is slightly detectable in WD tumors and barely detectable in MD/PD cSCC, that in turn display high levels of Survivin (BIRC5), which is predictive of a poor outcome in epithelial tumors [37], and of the chemokine CXCL-8, whose expression is associated with cancer progression [38] (Fig. 1i).