Immunohistologic detection of the epidermal growth factor receptor in human esophageal squamous cell carcinoma. Epidermal growth factor receptor (EGF-R) expression was studied immunohistologically in 38 patients with esophageal squamous cell carcinoma. The EGF-R was faintly expressed in basal and parabasal layers of normal esophageal epithelia and in cancer nests of 20 patients; it was strongly expressed in all areas of dysplastic epithelia and in cancer nests of 18 patients. The patients with strongly expressed EGF-R had lymph node metastases more frequently, and their prognosis was poorer than those with faintly expressed EGF-R. The EGF-R expression showed a mosaic pattern in 17 patients and a diffuse pattern in 21 patients. The patients with a mosaic pattern had lymph node metastases more frequently and a worse prognosis than those with a diffuse pattern. Expression of EGF-R in metastatic lymph nodes was similar to that in strongly expressing areas of primary cancers with a mosaic pattern. Thus EGF-R expression may be an important indicator for malignancies of esophageal squamous cell carcinomas because primary cancer cells with strongly expressed EGF-R metastasize to lymph nodes more frequently. 