A Case Report of a Poorly Differentiated Neuroendocrine Carcinoma Diagnosed in the Bone Marrow

Poorly differentiated neuroendocrine tumors are uncommon tumors of the GI tract and often diagnosed without the identification of the primary site. Here, we describe a case of poorly differentiated neuroendocrine carcinoma of unknown primary that is diagnosed by bone marrow biopsy. A68-year-old male patient presented with worsening back pain, hypercalcemia, anemia, and altered mental status. Initially, imaging favored multiple myeloma. However, a bone marrow biopsy revealed morphologic and immunohistochemical features of neuroendocrine origin.