A rare case of papillary cystadenocarcinoma of the sublingual gland was immunohistochemically studied. Regional lymph node metastasis was present at the time of diagnosis. Histologically, the tumor showed an invasive, cystic growth pattern and had a conspicuous papillary component. The predominant cell type of the tumor was a combination of tall columnar and large cuboidal cells. Immunohistochemical analysis indicated higher labelling indices of CD34 (31.9%) and Ki67 (40.1%) as compared with adenoid cystic carcinoma (ACC). Cyclooxygenase-2 expression was similar to that of ACC. These findings suggested a characteristic high-grade malignancy that required close follow-up.
