Osteoclast-type giant cell tumor of minor salivary gland with mucin-rich salivary duct carcinoma: a case report of unusual histology with immunohistochemical analysis

ObjectiveSalivary giant cell tumor (GCT) is exceedingly rare. This article presents an additional rare case of salivary GCT with salivary duct carcinoma (SDC).Study design and resultsThe patient was a 40-year-old Japanese male. The peripheral region of the tumor showed SDC and partly revealed a mucin accumulation with cancer nests, which was a mucin-rich variant of SDC. In the central region of the tumor, mononuclear ovoid tumor cells contained osteoclastic-type giant cells. SDC showed immunopositivity for gross cystic disease fluid protein-15 (GCDFP-15), androgen receptor (AR), and Her-2, whereas the giant cell lesion was negative for GCDFP-15, AR, and Her-2. Mononuclear cells in salivary GCT showed immunopositivity for epithelial membrane antigen and p53.ConclusionThe salivary GCT was thought to be neoplastic and derived from epithelial cells. The present case is the first de novo case of intraoral salivary GCT with a mucin-rich variant of SDC.