1993 年 5 巻 2 号 p. 43-51
Carcinoma in pleomorphic adenoma (malignant mixed tumors) is believed to originate from benign pleomorphic adenoma. A knowledge of the pathological and etiological features of carcinoma in pleomorphic adenoma is very important in the prevention of malignant change.
We examined carcinoma in plemorphic adenomas (5 males and 1 female) of the parotid gland treated in Okayama University Medical School Department of Otolaryngology from 1976 to 1992. These tumors accounted for 26.1% (6/23) of all parotid carcinomas.
The ratio of malignant mixed tumors to benign pleomorphic adenomas was 6/48 (11.1%). The mean age of the 6 patients was 57.8 and the mean duration before surgical removal was 21.7 years. Both values show a statistically significant difference from those of patients with benign pleomorphic adenomas (p<0.05). The malignancy of each case with carcinoma in pleomorphic adenomas was histologically diagnosed as adenocarcinoma in 6 cases. In 60% (3/5) of the malignant mixed tumors, overexpression of c-erb B-2 was detected by immunohistochemical staining, but there was no significant amplification of ras or p53. Moreover, 67% (2/3) of the c-erbB-2-positive malignant mixed tumors had neck metastasis. It is speculated that the overexpression of c-erbB-2 may play a role in the malignant change of plemorphic adenoma or in the progression of malignant mixed tumor.