Invasive poorly differentiated tumor, favor SCC.  Cannot see intercellular bridges well, nor cytoplastic squamous differentiation.  But if you look hard on slides, most time you will see focal squamous features such as squamous pearls, dense cytoplasm with whorling, or intercelluar bridges.  The exact location of the tumor is also important: SCC usually occurs in upper portion of the esophagus.  It seems that there is cellular molding as seen in small cell carcinoma.  It would be helpful to run a few immunostains to exclude small cell carcinoma or MM as proposed by other pathologists, if no squmous features are appreciated at all.