Text: Rue incense
In 2013, in the lab of the U.S. Centers for Disease Control and Prevention (CDC), pathologists experienced a moment of shock: They discovered a whole new type of cancer cell that no one had ever seen before.
The story begins in January of that year, when doctors treated an unusual patient in Medellín, Colombia. The 41-year-old male has suffered from symptoms such as fever, fatigue and weight loss for the past few months. He was diagnosed with HIV in 2006 but has not insisted on treatment ever since. His physical condition looks rather ominous: the massively multiplying HIV virus has destroyed the immune system, and the count of CD4+ T lymphocytes (the target of HIV attack) is far below normal. Not only that, but stool testing also revealed that he was infected with two parasites, including the tiny hymenolepis nana.
On CT examinations, worse conditions surfaced: abnormal nodular lesions appeared in the patient's lungs, liver and other parts, and many lymph nodes also appeared enlarged. Judging from the results of the pathological examination, the unfortunate patient seems to have also developed a tumor.
However, the patient's lesion tissue slices puzzled local doctors and CDC pathologists. These diseased tissues are filled with a large number of cells, and their disorderly appearance is in line with the typical cancerous characteristics, but the size of the cells is too small compared to human cancer cells. Even stranger, the two protein components that are widely present in human cells cannot be detected in these cells. These clues suggest that these "tumor-like lesions" are actually a non-human component.
Strange diseased cells put diagnosis and treatment at a standstill. A few months later, the patient's condition deteriorated and he died. Eventually, after in-depth investigations such as DNA testing, people finally verified the true identity of these mysterious cells. They are indeed not ordinary human cancers, but malignant cells from the parasite that patients infect, Tiny Membranium tapeworms. For pathologists, this is indeed a surprising result: they are no strangers to tapeworm cells, but this time, the malignancy has made the cells look so different that they cannot be observed at all when they are in the tapeworm. The findings were published in the New England Journal of Medicine on November 5, 2015.
Cells derived from the parasite undergo malignant changes and become "tumors" in the patient's body. Image courtesy of nejm.org
Infections of the tiny membranous tapeworm generally occur in the intestine, and it will enter the human body to infect the whole body itself is already a rare condition, and before that, people did not think that parasites can "infect" cancerous cells to human patients. It is unusual for cancer to be "contagious" directly between individuals, because it is reasonable to say that when cells from another individual or another species enter an animal, the immune system recognizes it as a "different person" and clears it. However, special circumstances can still occur. If the cells that cause the cancer happen to escape the immune system's scrutiny, or if the immune system has lost its normal function, foreign cancer cells may also camp. The patient's situation belongs to the latter, a large number of replicated HIV viruses seriously damage his immune function, so that tapeworm cancerous cells have the opportunity to take advantage of the void.
Of course, we don't need to worry about our bodies being occupied by these strange parasite cancerous cells right now. Such cases are very rare and occur only in immunocompromised patients, and there is no evidence that it can be transmitted in the population. The main significance of reporting this case is to remind doctors and medical researchers that cancer and infection can be linked in such a bizarre form. Elizabeth Murchison, a molecular geneticist at the University of Cambridge in the UK, said: "This paper is important because it shows a whole new type of disease process that may have been overlooked in the past. (Edit: Rain from the window)
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