Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum (T. pallidum). If left untreated, this infection progresses through several stages, potentially leading to severe complications affecting the heart, brain, and other organs. While other STIs are known to be oncogenic, the current scientific understanding is that T. pallidum is not classified as a direct cause of malignant cancer, unlike certain viruses like Human Papillomavirus (HPV).
The Current Scientific Consensus
The definitive answer is that no consistent, causal link between syphilis and cancer has been established in modern scientific literature. Unlike oncogenic viruses, T. pallidum does not possess the biological mechanism to integrate its genetic material into a host cell’s DNA, which is a common pathway for viral-induced malignancies. Therefore, it does not directly induce the malignant transformation of cells into cancer.
For example, syphilis was once believed to be a major cause of penile cancer, but subsequent studies identified Human Papillomavirus (HPV) as the central factor. While some studies have observed elevated rates of certain cancers, like oral cavity cancer, among people with a history of syphilis, the evidence does not allow for a conclusion of direct causality. The bacterium’s activity differs fundamentally from the cell-altering processes seen with true carcinogens.
Syphilis Progression and Benign Growths
The question about syphilis and cancer often arises because advanced infection stages produce physical manifestations that can resemble tumors. Untreated syphilis may progress to its tertiary stage, characterized by the formation of growths called gummas. These are soft, non-cancerous growths that can appear in various tissues, including the skin, bone, liver, and brain.
Gummas result from a delayed hypersensitivity immune response to the bacteria, leading to a specific type of chronic inflammation known as a granuloma. Microscopically, a gumma consists of a necrotic, firm center surrounded by a zone of inflammatory cells, including lymphocytes and plasma cells. These lesions are benign and represent a unique immune reaction rather than an uncontrolled proliferation of malignant cells.
Gummas can cause damage due to their size and destructive nature, sometimes mimicking tumors on imaging or clinical examination. The lesions can grow large enough to cause mass-like effects or local tissue destruction, such as in the liver or bone. This ability to form a destructive mass is why advanced syphilis is often referred to as “the great imitator,” as its symptoms can be misdiagnosed as other conditions, including cancer.
Indirect Risk Factors and Co-Infections
Although T. pallidum is not a direct carcinogen, the presence of syphilis can contribute to cancer risk through indirect mechanisms. The long-term, systemic inflammation that is characteristic of untreated syphilis can act as a general risk factor for various diseases, including some cancers. Chronic inflammation creates an environment where cellular damage and repair cycles are accelerated, which can increase the likelihood of genetic mutations leading to malignancy over time.
A more significant indirect link involves co-infection with the Human Immunodeficiency Virus (HIV), which is common among individuals with syphilis. Syphilis causes sores, which can increase the transmission and acquisition risk of HIV. HIV severely compromises the immune system, making the body highly vulnerable to cancers that are caused by other underlying viruses. For instance, people with HIV have a much higher risk of developing cancers like Kaposi’s sarcoma, which is caused by Human Herpesvirus 8 (HHV-8), or cervical and anal cancers, which are caused by HPV. In these cases, syphilis is a co-factor in the context of a weakened immune system, not the direct cause of the malignancy.
Elimination Through Treatment
Syphilis is a treatable infection, and prompt action eliminates the bacterial threat and associated risks. The standard treatment for syphilis at all stages is the antibiotic Penicillin G. For early-stage syphilis, a single dose of benzathine penicillin G is sufficient to cure the infection and prevent its progression to late-stage complications.
Treating the infection eliminates T. pallidum and prevents the development of destructive gummas and prolonged systemic inflammation. Even in cases of late or tertiary syphilis, penicillin therapy can resolve the infection and halt tissue damage. Early diagnosis and complete treatment remove the source of the infection and eliminate the possibility of severe outcomes.