In the case of poorly differentiated carcinoma, high-molecular-weight cytokeratin (e.g., CK5/6), p63, and/or p40 (which are all typically positive in squamous cell carcinoma) may help differentiate squamous cell carcinoma from adenocarcinoma and basaloid squamous carcinoma of the esophagus from the rare adenoid cystic carcinoma. Here, KRT5 is linked to squamous cell carcinoma.