A Rare Case of Metastatic Heterogeneous Poorly Differentiated Neuroendocrine Carcinoma of Ileum: A Case Report and Literature Review

Neuroendocrine neoplasms (NENs) represent a diverse group of tumors arising from neuroendocrine cells. Current World Health Organization (WHO) classification is based on tumor differentiation and grade defined by mitotic rate and/or Ki-67 index to determine prognosis and treatment options. However, some NENs do not meet WHO pathology criteria due to morphologic heterogeneity and this leads to management challenges. WHO defines poorly differentiated NENs of the gastrointestinal tract as having morphologically large or small cell features with marked elevation of Ki-67. We present a unique clinical case that does not fit either growth pattern and also has heterogeneity with a well-differentiated component. This case report and literature review highlights the current limitations of the WHO classification of small bowel NENs and the subsequent challenges in management decisions for the patients.