Gene expression profiling and its use in adenocarcinomas of unknown primary origin: A case report.

Carcinomas of unknown primary origin account for 3-5% of all malignancies. The current literature suggests that metastatic dissemination is able to occur in the absence of primary tumor growth. In metastatic disease that is difficult to diagnose, the origin usually remains unknown even after an exhaustive evaluation of immunohistochemistry (IHC) markers. In the current study, a 49-year-old male presented with lymph nodes metastases of unknown origin. The excisional biopsy of an inguinal node revealed an adenocarcinoma growth pattern, but the IHC could not determine the primary origin. A gene profiling test was performed to complete the diagnosis and a salivary gland adenocarcinoma was diagnosed with 90% probability. Subsequently, the patient underwent appropriate chemotherapy for salivary gland adenocarcinoma, and exhibited an improved partial response. The present case study highlights the importance of an accurate diagnosis of the primary tumor and the use of all the current tools available in order to provide patients with the best treatment possible.