A doctor in China has warned household cooks not to use dirty knives and cutting boards when preparing food.

“Do not let carelessness in your kitchen become a loophole for parasites,” the doctor said after surgically removing a “cyst” from a patient at the Shenzhen People’s Hospital in Guangdong province, according to the South China Morning Post (SCMP).

The patient, surnamed Wang, came to the hospital complaining of pain from a swollen lump in her arm the size of a quail egg. When doctors operated on the lump, they found two 10-centimeter-long living worms under the skin and removed them, SCMP reports.

According to the doctors, the parasite called “sparganum” entered her body as microscopic eggs while likely attached to a knife or cutting board that she used for chopping live frogs and cold dishes. She then ate the contaminated food and the parasite eggs started growing inside her body one year ago.

Meanwhile, a 60-year-old Spanish man went to the hospital complaining of severe headaches the past two weeks.

CT scans of the patient’s head showed multiple abnormal spots that looked like tumors, leading doctors to suspect he had advanced brain cancer, Fox News reports, citing the rare case published in the CDC journal, Emerging Infectious Diseases (EID).

After a whole body scan, a colonoscopy, and specialized imaging failed to detect cancer anywhere in the patient’s body, a more detailed MRI was performed and several fluid-filled cysts in the brain, some of which contained tapeworms, were discovered, according to Fox News.

A blood test confirmed the diagnosis of neurocysticercosis and the man was treated with the antiparasitic medications albendazole and praziquantel to “dissolve” the tapeworms.

He recovered with no complications, according to the case report, which suggested that the patient may have accidentally ingested microscopic tapeworm eggs years earlier while working a construction job with migrant co-workers from regions where neurocysticercosis was endemic.

The EID said people can catch pork tapeworm by eating undercooked infected meat or accidentally swallowing the parasite’s eggs through food and water contaminated with feces, sending the larvae into the bloodstream, where they may form cysts in the brain and other organs, according to Fox News.