RESUMO
INTRODUCTION: NeuroEndocrine Neoplasms (NENs) are rare and can originate from any epithelial organ. We describe a very rare case of retroperitoneal metastasis from a non-functioning neuroendocrine tumor of the ethmoid region and focus on the various issues related to NENs, from their nosological classification up to the most recent acquisitions in the diagnostic and therapeutic field. PRESENTATION OF CASE: A woman presented with a mass in the right retroperitoneal area that infiltrated liver and kidney. The anamnestic data showed a previous undifferentiated small cell tumor of the left ethmoid-nasal-orbital region. The mass was removed surgically and the definitive histological examination revealed a non-functioning undifferentiated malignant small cell neoplasm. DISCUSSION: NENs represent a chapter of oncology whose systematization remains difficult. The lack of hormonal syndrome in Biologically Inactive Neuroendocrine Tumors (BINTs) may delay the diagnosis. Clinical manifestations relate to the size and location of the neoplasm. Small cell NeuroEndocrine Carcinoma (NEC) of the ethmoid-nose-orbital region is an extremely rare occurrence and generally the most frequent metastatic localization is represented by the larynx. CONCLUSION: This case highlights the contradictions typical of NENs and only new scientific acquisitions in the histopathological field can help us in the future. Surgery remains the only possibility of treatment and diagnosis of large masses of inactive NENs. This is the only case in the world of metastasis from NEC of the nose-orbital region in the retroperitoneum.