How unknown is metastatic carcinoma to cervical lymph nodes from an unknown primary?

The term metastatic carcinoma to cervical lymph nodes from an unknown primary includes a small group of tumors that present themselves with metastases to the cervical nodes, and in which diagnostic methods do not reveal the primary source of these metastases. Histologically, in most cases, these are metastases of squamous cell carcinoma. Carcinomas of unknown primary metastatic to cervical nodes account for < 5% of carcinomas of unknown primary and < 5% of head and neck cancers. The optimal treatment has not yet been defined. In the absence of distant metastases, the intention of treatment is curative. Patients are treated mostly with combined approaches including surgery, radiotherapy, or concomitant chemoradiotherapy. Radiotherapy is part of the treatment algorithm in most of the referenced works and includes irradiation of the mucosal sites of the pharyngeal axis as a potential localization of the primary tumor and unilateral or, more often, bilateral irradiation of the neck. Due to the higher risk of late toxicities observed, individualization of irradiated volumes based on the extent of the disease or other clinical parameters is a rational way to reduce these risks.  Purpose: The presented work discusses the treatment options for patients with metastatic carcinoma to cervical lymph nodes from an unknown primary. Furthermore, the work reports on the high effectiveness of curative radiotherapy in this group of tumors.