A Neuroendocrine Tumor of Unknown Primary Origin that Responded to Treatment Based on Tumor Grade Progression.

The standard chemotherapies for neuroendocrine tumors (NETs) are somatostatin analog (SSA) and targeted-agents for NET G1/G2 and platinum-based chemotherapy for neuroendocrine carcinoma (NEC), classified according to the WHO criteria of 2010. We report a case of NET, in which tumors were successfully treated with platinum-containing chemotherapy after remarkable progression with SSA. A 46-year-old man with multiple lymph nodes and liver metastases of unknown primary origin was diagnosed with NET G2 based on the examination of a biopsy specimen. His tumors were stable with SSA for a year, but rapidly became enlarged. A second biopsy revealed NEC. He received cisplatin plus etoposide, and his tumors showed a marked reduction in size.