S3411 Extensive Hepatic Lesions From a Primary Duodenal Neuroendocrine Carcinoma in a Young Male

Introduction: Neuroendocrine neoplasms (NEMs) are relatively rare, accounting for 0.5% of newly diagnosed malignancies. NEMs can be found throughout the body with two-thirds arising in the GI tract and incidence increasing among duodenal NEMs. These malignancies have a female predominance and generally occur in the 6th decade of life. This is a case of advanced metastatic disease from an unexpected duodenal neuroendocrine carcinoma in a healthy young male. Case Description/Methods: A 29-year-old male, with no PMH, acutely developed sharp RUQ abdominal pain. Prior to this, he was in his usual state of health. In the ED, the patient was hemodynamically stable with tenderness to palpation in the RUQ. Initial labs showed WBC 12.10 × 103/uL, Hgb 11.7 g/L, AST 55 U/L, ALT 173 U/L, ALP 127 U/L, and TBIL 0.8 mg/dL. CT A/P showed multiple well-circumscribed liver lesions, largest measuring 8.6 × 7.8 cm, with portal venous invasion (Figure A). CA 19-9 and CEA were negative. There was elevation of AFP 1,577 ng/mL and LDH 817 U/L, but negative hCG. A1AT, ANA, AMA, ASMA, ALKM, and ceruloplasmin were negative. Liver biopsy showed a poorly-differentiated malignant neoplasm of unknown primary. EGD was performed revealing a fungating mass in the second portion of the duodenum (Figure B). Pathology favored a high-grade poorly-differentiated neuroendocrine carcinoma (Figure C). He was discharged with palliative cisplatin/irinotecan initiation. Discussion: Gastrointestinal NEMs have been increasing in prevalence due to improved awareness. When carcinoid symptoms are absent, detection is dependent on imaging and endoscopy after the patient presents with complications from metastasis or mass effect. Following biopsy, GI NEMs are classified by WHO 2010 criteria into 3 groups based on mitotic count and Ki-67 index. Group 3 tumors are classified as poorly-differentiated neuroendocrine carcinomas with Ki-67 >20% with higher rates of angioinvasion and metastatic potential. Lymph node metastasis occurs in 60% of duodenal NETs, while liver mets occur in < 10%. In our case, the patient’s Ki-67% index was >90%, characterizing it as a Group 3 NEM. Characterization is important given the impact on prognosis and treatment. Group 3 NEMs have the overall worst prognosis. Since >90% of duodenal NEMs do not cause a clinical syndrome and are not associated with metastatic disease, surgical or endoscopic resection is preferred. However, if there is metastatic disease or high-grade histologic features, chemotherapy is the mainstay of treatment.Figure 1.: A, CT A/P with multiple large heterogeneously enhancing liver lesions concerning for metastatic malignancy of unknown primary (B) Large fungating mass located in the second portion of the duodenum (C) Duodenal mass, H&E stain, 20×, high-grade poorly differentiated epithelial malignancy composed of nested cells with indistinct nucleoli, moderate eosinophilic cytoplasm, and brisk mitosis.