Patient: Male, 66 years old, admitted to the hospital for “discovery of a right breast lump with paroxysmal swelling and pain for more than one year”. More than a year ago, the patient inadvertently detected a bean-sized lump in the areola of his right breast, which was slowly increasing in size. The localized swelling and pain was often accompanied by a significant increase in the size of the lump after drinking alcohol or eating seafood, and the skin of the breast was reddened, which resolved on its own after a few hours, with a slight decrease in the size of the lump. Infrared examination of the breast showed “localized thickened and tortuous blood vessels in the right breast”. The patient grew up in Zhenjiang, Jiangsu Province, and later worked and settled in Shanghai. She denied any history of staying in the infected area, and was of Hui ethnicity, with a preference for beef and mutton, and no history of eating raw meat. Six years ago, there was a similar mass on the left abdominal wall, which did not recur after resection, and the pathology was unknown. The patient was admitted to the hospital and underwent “right breast lumpectomy” under local anesthesia, during the operation, a lump was seen in the breast tissue, which was solid, and the demarcation of the breast tissue was unclear, without peritoneum, and there was an irregular sinus tract in the lump, and the internal diameter of the sinus tract was balanced, about 0.4 cm2. The lump was completely excised, and a nematode was found inside the sinus tract after dissecting, which was a living organism, and the eggs of nematode were not seen in the lump. No eggs were found in the mass. Pathological examination showed that the mass was “fibrous hyperplasia and chronic inflammatory tissue”. The nematode was about 0.4×15 cm, with a white head, a forked head end, obscure body segments, and a flattened body, which was judged by the Parasitology Department of the School of Medicine to be a “Mannheimer’s tapeworm, Schizosaccharomyces pilaris”. [The larvae of the tapeworm Spirometra mansoni are called schizothoracic larvae, which develop from protozoa, and they have a great ability to move around. When animals swallow intermediate hosts such as frogs or snakes containing schizothoracic larvae, the schizothoracic larvae are unable to develop into adult worms inside the intestine, and then they penetrate out of the intestinal wall and parasitize the various parts of the abdominal cavity, the muscular layer, and the subcutaneous tissues. Adult tapeworm parasitism in humans is rare, while cases of schizothoracic larvae are often found in some areas, mostly due to the use of raw frog meat to apply wounds, or swallowing live frogs, snakes, and undercooked cattle, sheep, pork, etc. caused by schizothoraciae directly invading from the wounds, or due to accidental ingestion of schizothoraciae, protozoa and become infected. Schizosaccharid larvae can be parasitized in various parts of the human body, and like to migrate in the human body, the local destruction of the infested tissues is more obvious, with the skin, eyes and abdomen as the common, and parasitized in the mammary gland tissues of the retrieval of the domestic has not yet been reported, and the most recent foreign report is a case that occurred in South Korea more than 20 years ago, so it is difficult to take into account the preoperative diagnosis of the mammary gland lumps in the clinic and led to the misdiagnosis. In addition to removal of the mass, deworming is also necessary to remove the parasites and eggs from the rest of the body that do not cause obvious symptoms.