[Macrocytosis of red blood cells and early arthritis positive for rheumatoid factor such as initial manifestations of a neuroendocrine gastrin-secreting gastric tumor.].

Neuroendocrine tumors (NETs) represent uncommon tumors arising from the excessive proliferation of enterochromaffin-like (ECL) cells (so-called Kulchitsky cell). Gastric NETs (GNET) represent less than 2% of all NETs and less than 1% of all stomach neoplasms. In particular, gastric NETs type 1 (associated to chronic atrophic gastritis and hypergastrinaemia) is the more frequent one, accounting for 70-80% of all GNET. A macrocytic anemia is a frequent manifestation of GNET type 1. The possibility that macrocytic anemia appear during therapy with methotrexate (MTX) is widely documented. Similarly, MTX can determine gastric atrophy. We describe the case of a patient with rheumatoid factor-positive early arthritis (EA) in which the appearance of macrocytic anemia during treatment with MTX led to the recognition of a GNET type 1, until then asymptomatic. The endoscopic eradication of polypoid formations forming the GNET, the immediate suspension of MTX and therapy with octreotide long-action determined the complete remission of arthritis. This remission is maintained until today. According to our knowledge, the possibility that an EA may represent a paraneoplastic manifestation of GNET has never been described.