Clinical and immunohistologic typing of salivary duct carcinoma: a report of 50 cases.

BACKGROUND: Due to the low incidence of salivary duct carcinoma (SDC), only limited data in regard to the biologic behavior of this tumor and its immunohistochemical characteristics are available. The authors analyzed the clinical, molecular, and genetic profile of SDC and identified prognostic factors.

METHODS: The follow-up of 50 patients with SDC was obtained and paraffin-embedded tumor samples were examined immunohistochemically. In all samples, the expression of Ki-67, HER-2, and the oncoproteins p16 and p53 was examined immunohistochemically, followed by a mutation analysis of p16 and p53. The survival rate was calculated by the Kaplan-Meier method and prognostic variables were analyzed with the log-rank test.

RESULTS: SDC predominantly effected male patients (66%) in their 7th decade of life. SDC mainly occurred in the parotid gland (78%; submandibular gland, 12%; minor salivary glands, 10%). Approximately two-thirds of the patients (33 of 50) presented with a T3/T4 tumor. In 28 patients (56%), cervical lymph node metastasis was present at the time of diagnosis. Local disease recurrence was observed in 48% of patients an average of 17.4 months after initial treatment. Distant disease metastasis developed in 48% of patients an average of 29 months after initial treatment. The average overall survival period was 56.2 months. In the current study, 20.6% of the probes with positive HER-2/neu expression were (+++) positive. p53 was expressed in 83.9% of the tumor samples. In 11.8% of the tumor samples, there was a lack of p16 expression.

CONCLUSIONS: Mutations of the p53 gene were more frequent in tumor samples with (++) and (+++) immunoreactivity and mainly affected exons 7 and 8. A mutation of the p16 gene was only found in 1 tumor sample. Expression of HER-2/neu and p53 was statistically linked (P < 0.05) to early local disease recurrence, distant disease metastasis, and survival rates.