CARCINOMA IN BASAL-CELL ADENOMA OF THE PAROTID-GLAND

Malignant transformation of basal cell adenoma (BCA) of the parotid gl and is rarely reported, and when occurred, may principally become mani fest as a malignant basaloid tumor, i.e. basal cell adenocarcinoma or adenoid cystic carcinoma. We describe herein three cases of non-basalo id carcinoma arising in BCA. The incidence of this malignant tumor was 0.2% of all parotid gland tumors and 4.3% of BCAs in our series. One case was salivary duct carcinoma showing histologic evidence of transi tion between malignant and benign elements. The remaining two cases we re well-encapsulated parotid gland tumors, which were composed of BCA and scattered foci of malignant transformation. Malignant components w ere adenocarcinoma, not otherwise specified (NOS), and sometimes inter mixed with neoplastic myoepithelial cells included BCA cells. These tw o cases were regarded to be intracapsular carcinoma in BCA. BCA compon ents showed solid, tubular and trabecular arrangements. The patients' prognosis was quite variable among these three cases; the first case d ied of disease after 27 months, whereas the latter two cases are alive and well for 4 and 10 years after surgery. Ki-67 labeling index indic ated that cell proliferative activity was at least five times higher i n carcinomas than BCAs. Non-basaloid carcinomas such as salivary duct carcinoma or adenocarcinoma, NOS, do develop in BCAs as in the case of a pleomorphic adenoma with malignant transformation, though the incid ence may be extremely rare.