Salivary duct carcinoma in the sinonasal tract.

Salivary duct carcinoma (SDC) is an uncommon malignant tumor, characterized by aggressive behavior and poor prognosis. SDC usually arises from ductal epithelium of the major salivary glands, and it is quite infrequent elsewhere. We present a rare case of a 73-year-old man with SDC, which is possibly originated from the paranasal sinuses or the lacrimal system. Microscopic evaluation revealed that the tumor cells, with pleomorphic nuclei and abundant eosinophilic cytoplasm, formed cell nests and duct-like structure. A cribriform growth pattern was also seen. Immunohistochemical staining was positive for cytokeratins (CAM 5.2 and 34betaE12), gross cystic disease fluid protein 15 (GCDFP-15), and androgen receptor protein, while p63 and involucrin were negative. The patient already had multiple metastasis of the tumor in the lung at diagnosis, and he could not undergo definitive surgical procedures, because of severe restrictive lung disease. Although SDC in the sinonasal tract is quite rare, SDC should be in the differential diagnosis in these regions, due to its aggressive behavior and poor prognosis.