Poorly Differentiated Neuroendocrine Tumors.

Poorly differentiated neuroendocrine carcinomas of the gastrointestinal tract are rare and limited data are available to guide treatment. These tumors have been treated akin to small cell lung cancer given the histologic similarities. Their pathology is complex. Over the last decade, these tumors are shown as likely a distinct disease entity that is more heterogeneous than accounted for by the current classification system. This article discusses the epidemiology, prognosis, clinical presentation and pathologic nuances and provides a review of the existing clinical data in poorly differentiated neuroendocrine carcinomas and small cell lung cancers.