TMEM45A (transmembrane protein 45A) is a transmembrane protein with protein binding capability that functions as a pro-fibrotic and oncogenic factor across multiple disease contexts. In fibrotic diseases, TMEM45A promotes pathological remodeling: it regulates renal fibrosis through the Jagged1/Notch pathway 1, drives atrial fibrosis in atrial fibrillation patients with systemic lupus erythematosus 2, and is implicated in mitophagy dysfunction in rheumatoid arthritis 3. In cancer, TMEM45A is consistently upregulated and promotes malignant progression. It enhances multidrug resistance in colorectal cancer by suppressing the TGF-β signaling pathway and driving epithelial-mesenchymal transition 4, increases palbociclib resistance in HR+ breast cancer via AKT/mTOR pathway activation and enhanced glycolysis 5, promotes ovarian cancer proliferation and invasion through TGF-β/RhoA/ROCK2 signaling 6, and serves as a reliable independent prognostic marker in gastric cancer 7. Additionally, TMEM45A-expressing fibroblasts in the tumor microenvironment facilitate colorectal cancer liver metastasis by participating in migrasome-mediated immune reprogramming 8. Collectively, TMEM45A represents a potential therapeutic target across fibrotic and malignant diseases.