FNDC3A (fibronectin type III domain containing 3A) is a fibronectin type III domain-containing protein with multifaceted roles in development and disease. Structurally, it comprises a proline-rich N-terminal region, eight type III-fibronectin modules, and a transmembrane helix, localized primarily to Golgi vesicles and the ER 1. In normal physiology, FNDC3A mediates spermatid-Sertoli cell adhesion during spermatogenesis and regulates extracellular matrix formation critical for fin development and regeneration 23. FNDC3A forms a complex with FAM46C that modulates ER-associated protein trafficking, secretion, and autophagy pathways 4. In multiple myeloma, loss of FNDC3A expression occurs in some cell lines, and reconstitution triggers apoptosis through impaired autophagy and protein aggregate accumulation 4. In gastric cancer, FNDC3A functions as a tumor suppressor in the SNHG14/miR-206/FNDC3A regulatory axis, with elevated FNDC3A expression associated with better prognosis 5. Conversely, in triple-negative breast cancer, high FNDC3A expression correlates with poor overall survival and promotes epithelial-to-mesenchymal transition via YAP1 pathway activation 6. These context-dependent roles suggest FNDC3A as a potential therapeutic target across multiple cancer types 7.