Immunopathology of phenotypic change on human parotid gland adenocarcinoma

Immunopathological analysis was made of phenotypic change in a recurrent parotid gland adenocarcinoma occurring in a patient with a long clinical course of 30 years or more. At the first and second operations, in 1959 and 1978, the resected parotid gland tumors were diagnosed histopathologically as acinic cell carcinoma. However, 11 years after the second operation, in 1989, the resected recurrent tumor showed a microscopically phenotypic change towards adenocarcinoma with typical tubular arrangement. At the last operation in 1991, histopathological examination of the tumor revealed adenocarcinoma with diffuse oncocytic change in association with cervical lymph node metastasis. These findings suggest that phenotypic change may occur in vivo among human neoplasms during a long period, which may be related to the cytodifferentiation in the salivary gland tumor.