Bone Marrow Infiltrate by a Poorly Differentiated Neuroendocrine Carcinoma

We report a rare case of bone marrow infiltrate by a neuroendocrine carcinoma. The patient was a 66-year-old man who presented with anemia and thrombocytopenia and with a leukoerythroblastic picture on blood films. A bone marrow biopsy revealed extensive tumor infiltrate with morphological and immunohistochemical features of neuroendocrine origin. There were also multiple nodular lesions in the liver, which showed the same pathology as that in the bone marrow. Since none of the lesions could be identified as the primary tumor, the patient was diagnosed to have a poorly differentiated neuroendocrine carcinoma of unknown primary site.