Something that is not appreciated by most people—I include in this students, oncologists and scientists—is that cancer is unique among the major diseases in being a disease of the cell. Other diseases are diseases of individual organs or organ systems, and generally reflect problems that arise from inflammation, deterioration or infection. But cancer is unique in being a disease of the cell.
What do I mean by this? If one takes a tumor cell from a Petri dish in which tumor cells are growing and transfers it to another Petri dish, an entirely new colony of tumor cells will arise. Likewise, if one takes a tumor cell from a tumor growing in a mouse and transfers it to a healthy mouse, again a new tumor will arise. This illustrates that all the information necessary to form a cancer is contained in that cell. If you take a cell from the heart of a mouse with a myocardial infarction and transfer it to a healthy mouse, nothing will happen. Similarly, if you take a cell from the joint of a mouse with rheumatoid arthritis and transfer it to a healthy mouse, again nothing will happen. Only in cancer does the cell have this property of transferability.
Can the same phenomenon happen in humans? There are multiple circumstances under which this principle has been demonstrated. There are several anecdotes that are circulating on the internet and in chat lines that discuss cases of surgeons who cut themselves while operating on patients with tumors. Some months/years later, these surgeons developed malignancies on their hands at the site of the cuts. The cell type of the new tumor in the surgeon was consistent with the tumor of the original patient. At least one of the cases I read about that occurred in 2016 was a melanoma.
Another such case was published in 1996 in the New England Journal of Medicine regarding a 32-year-old man who underwent surgery for a malignant fibrous histiocytoma of the abdomen, a type of sarcoma. During surgery, the 53-year-old surgeon injured his palm. The wound was disinfected and cleaned but five months later he developed a 3cm hard lesion at the site which proved to be a malignant fibrous histiocytoma identical to the original tumor. It was excised and fortunately never recurred.
Fifteen years ago, I was the camp doctor at Camp Seneca Lake in the Poconos. One Shabbat afternoon, I ended up chatting with a weekend visitor to the camp, a woman in her early 40s, who upon learning that I was an oncologist told me her own personal cancer tale. Some years earlier she had undergone a liver transplantation for liver failure secondary to a benign liver condition. Two years later she developed lung metastases of unknown origin. A biopsy showed that these were lung cancer (she was a nonsmoker) that were determined to have originated from the donor of her liver. Apparently, the donated liver had unwittingly carried microscopic tumor cells from an undiagnosed cancer in the donor. These cells now had the opportunity to proliferate and metastasize in her immunosuppressed environment. (She was on immunosuppressant drugs.)
Luckily for her, it is relatively easy to treat such cancers—simply discontinue taking the immunosuppressant drugs and the body’s immune system will reactivate, recognize these tumor cells as “other” and destroy them. Of course, it will destroy her donated liver as well, so the woman required a new liver transplant. Such transplant-carried tumor cells and subsequent cancers have been reported numerous times and illustrate the concept of cancer as a disease of the cell.
Another context in which cancer cells have been transmitted from one human to another and had the opportunity to proliferate and establish tumors is in maternal-fetal transmission. It is not uncommon for mothers to have cancer, known or unknown, at the time that they are pregnant. The mother and the fetus have independent blood streams. There is supposed to be a barrier between the two blood streams that filters out toxic or harmful substances from passing from the mother to the fetus. Nonetheless, this system is not inviolate. There are 30 to 40 published case reports (which suggests that it has occurred significantly more frequently) of tumors that have passed from the mother to the fetus. These have generally been either melanomas, leukemias or lymphomas. In most instances, they have been recognized because the tumors have had XX chromosome makeups in male infants (XY chromosomes).
The astute reader may wonder why the fetus/neonate did not reject the tumor as foreign. But it is now recognized that neonatal immune systems are underdeveloped and immature until weeks/months after birth and so would not automatically reject any antigens presented to them in utero. Actually, cancers occur in pregnant women with quite high frequency so the number of times in which transplacental transmission of cancer has occurred seems to be quite rare. Nonetheless, it does happen.
We will continue this important topic in our next episode of Thoughts on Cancer.
Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.
This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.