More than a year ago, a large rash suddenly appeared on Mr. Liu’s legs, which soon developed into blisters, vesicles, necrosis, and unbearable itching and pain. In view of the fact that Mr. Liu’s rash was somewhat bizarre and that he had sought medical help everywhere to no avail, the doctor recommended that he be admitted to the hospital for a full examination. First, abdominal ultrasound and blood tests were done, with no specific findings. He was also given a microbiological culture of the skin tissue on his body, and a large number of drug-resistant Staphylococcus aureus were found. Could these drug-resistant Staphylococcus aureus be the culprit? I suddenly remembered a paper I had read that pointed out that some rash skin diseases are associated with increased glucagon. In turn, glucagon elevation is caused by secretory tumors of the pancreas. Is Mr. Liu’s disease caused by pancreatic secretory tumor? The examination suggested that there was a 5.5×4.3 cm mass in the tail of Mr. Liu’s pancreas, which was first considered as pancreatic cancer. Pathological biopsy confirmed that it was pancreatic endocrine carcinoma, which was fortunately found quite early. After surgery, the rash slowly faded away like a flood. Tumor is a “monster” that can affect the function of various organs in the body, and the skin is a “window” that can show potential signals of the disease. This skin disease like Mr. Liu’s is clinically called necrolytic loosening erythema migrans, which can also be called paraneoplastic skin disease. It is associated with increased glucagon catabolism due to the secretion of biologically active substances by pancreatic tumors. The main manifestation is an erythematous papule with annular extension that may develop into blisters with central erosion and necrosis, leaving hyperpigmentation after healing with pain and itching. Although skin diseases are annoying, the presence of paraneoplastic signs can help doctors to detect malignant tumors in the body early so that they can be treated in time.