Metastatic lung cancer with occult primary site: a difficult diagnosis

Occult primary non-small cell lung cancer (OP-NSCLC) is a relatively rare entity that brings difficulties in diagnosis and treatment. Accurate diagnosis depends on biopsy specimens. Often, repeated biopsies are required. Here we report a patient who underwent 3 rounds of biopsy of her cervical superficial enlarged lymph nodes to get a final diagnosis of occult metastatic lung cancer. There was no evidence of primary lesions in the lung. The patient was treated with targeted chemotherapy and survived 4 years. We emphasize the importance of repeated biopsies or resection biopsy for a definitive diagnosis. Though molecular technologies and imaging may identify a primary site, some cases have occult primaries. Adjunct examination methods such as immunohistochemistry and/or molecular methods are valuable for definite diagnosis and guiding treatment.