Rare Case of High Grade Neuroendocrine Carcinoma Found on Bone Marrow Biopsy: A Case Report

Background: Neuroendocrine neoplasms (NENs) comprise a wide-ranging group of abnormal neoplasms with atypical presentations, from primary localized disease to extensive metastasis, reaching the bone and brain. The NENs are divided into two major groups: neuroendocrine tumors (NETs), which are well-differentiated tumors of any grade, and neuroendocrine carcinomas (NECs), which are poorly differentiated, high-grade cancers with a high risk of morbidity and mortality. The challenge of diagnosing NENs early, particularly prior to metastasis, highlights the importance of further studying these diseases. We present a case of aggressive metastatic neuroendocrine carcinoma of a gastroin-testinal/pancreaticobiliary origin. Case summary: A 54-year-old male with a past medical history of hypertension and left total hip replacement presented with generalized weakness, dyspnea on exertion, decreased appetite, and fatigue for one month. Initial laboratory findings noted a hemoglobin level of 3.1 g/dL and a platelet count of 9 pound 109/L. CT scan findings revealed a splenic infarct, lytic bone lesions, and small bilateral occipital hemorrhages. Bone marrow biopsy was consistent with meta-static, high-grade, poorly differentiated neuroendocrine carcinoma favoring a gastrointestinal/pancreaticobiliary origin. The patient expired shortly after starting chemotherapy due to the extensive disease. Conclusion: Neuroendocrine neoplasms may be discovered late in their course with distant metastatic spread and thus have a poor prognosis. This case report and literature review describes the presentation of metastatic high-grade neuroendocrine carcinoma in a patient presenting to a community hospital, and reviews the current literature and guidelines on neuroendocrine carcinomas.