Dedifferentiated acinic cell carcinoma of the parotid gland: a distinct rarely described entity.

A case of dedifferentiated acinic cell carcinoma of the parotid gland is presented. A 46-year-old man presented with a parotid gland mass. At surgery the tumor was found adherent to the temporal bone and cervical adenopathy was present. Treatment included radical parotidectomy and intraoperative radiotherapy. Histologically, the tumor was a composite of a usual low-grade acinic cell carcinoma and high-grade, poorly differentiated carcinoma. Cervical lymph node metastases were composed entirely of high-grade carcinoma. Immunohistochemically, both low- and high-grade malignant components were negative for p53 oncoprotein expression. Moreover, polymerase chain reaction and nonisotopic single-stranded conformational polymorphism analyses were consistent with a germ line configuration of the p53 gene, exons five through eight, in both low- and high-grade elements of the tumor. The literature on this unusual variant of acinic cell carcinoma is reviewed.