HEG1 and carcinoma: Therefore, HEG1 has proven to be of excellent value as a mesothelial lineage marker, once again, and could be a useful addition to the current immunohistochemical panel of biomarkers, showing a diagnostic specificity of 92.3% in distinguishing PEM and PBM from all carcinomas and 98.7% in distinguishing PEM and PBM from pulmonary carcinomas.