Hyperferritinemia as a Clue to Neuroendocrine Carcinoma.

Ferritin is the protein that serves as the main mechanism for iron storage. It can also be an acute-phase reactant, which may rise in response to inflammation, infection, injury, autoimmune disease, or malignancy. Therefore, when evaluating ferritin levels, it is important to consider both iron storage and potential underlying conditions that could cause hyperferritinemia. We report a case of an elderly man in his late 80s who had elevated ferritin levels for years before ultimately being diagnosed with metastatic neuroendocrine carcinoma. The initial diagnosis was suspected to be due to iron overload from iatrogenic causes, but despite discontinuation of iron supplementation, the patient continued to have hyperferritinemia. Broad differential diagnoses were considered, including hereditary hemochromatosis, sideroblastic anemia, thalassemia, viral infection, hereditary hyperferritinemia, myelodysplastic syndromes with ineffective iron regulation, hemophagocytic lymphohistiocytosis, and other autoimmune phenomena. However, workup was negative. Ultimately, bone marrow biopsy was performed, which revealed poorly differentiated metastatic carcinoma with neuroendocrine differentiation.