An esophageal carcinoma characterized by the absence of microscopic features of squamous differentiation. However, there is immunohistochemical evidence of squamous differentiation. The disease is MONDO_0018481 (undifferentiated carcinoma of esophagus). Also known as: esophageal undifferentiated carcinoma, esophagus undifferentiated carcinoma, oesophagus undifferentiated carcinoma, undifferentiated esophageal cancer, undifferentiated esophageal carcinoma.