China has one of the highest incidences of nasopharyngeal cancer in the world, and about 80% of nasopharyngeal cancers in the world occur in China. The incidence rate of nasopharyngeal cancer is also high among Chinese living in other parts of the world. There are obvious regional differences in the distribution of nasopharyngeal cancer in China, with the high incidence centers being Zhaoqing, Foshan and Guangzhou areas in central Guangdong and Wuzhou area in eastern Guangxi, which are connected to each other and gradually decrease in the surrounding areas. Residents in Guangdong Province mainly speak three dialects, namely Guangzhou, Hakka and Minnan, and the susceptible population in the above-mentioned high incidence areas are mainly residents who speak Guangzhou dialect. Nasopharyngeal cancer is predominantly found in men, about twice as often as in women. Nasopharyngeal cancer can occur in all age groups, mostly between 30-50 years old.
Causes and risk factors of nasopharyngeal carcinoma 1. EBV infection EBV-infected cells can produce a variety of EBV-specific antigens, including early antigen EA, shell antigen VCA, membrane antigen MA, and nuclear antigen NA, and so on. The human body will produce various antibodies corresponding to EBV infection. The positive rates of EBV EA-IgA and VCA-IgA antibodies in nasopharyngeal carcinoma patients were 96% and 81.5%, respectively, indicating that these two antibodies can be used as serological diagnostic markers for nasopharyngeal carcinoma. However, the positive rate of EA-IgA antibodies in normal subjects was higher and less specific than VCA-IgA in the diagnosis of nasopharyngeal carcinoma. The incidence of nasopharyngeal cancer in VCA-IgA-positive people is more than 40 times that in negative people, in other words, VCA-IgA-negative people rarely develop nasopharyngeal cancer.
2.Environment and diet Environmental factors are also a cause of nasopharyngeal carcinoma. It is reported that among Chinese Americans, the second generation born in the United States has a lower risk of developing nasopharyngeal cancer than the first generation born in Asia, while Caucasians born in California in Southeast Asia have a higher risk of developing nasopharyngeal cancer than those born in the United States. In Guangdong, it was found that rice and water in areas with high incidence of nasopharyngeal carcinoma had higher levels of the trace element nickel than those in areas with low incidence. Nickel was also found to be high in the hair of nasopharyngeal carcinoma patients, and nickel may be a cancer-promoting factor. Dinitrosopiazine DNP is associated with the development of nasopharyngeal carcinoma. The consumption of salted fish and pickled food is a high risk factor for nasopharyngeal carcinoma in southern China, and is related to the age of eating salted fish, the duration and frequency of consumption, and the cooking method. This is related to the high concentration of nitrosamine compounds in salted fish and pickled products.
3.Genetic factors There are racial and family clusters of nasopharyngeal cancer patients, and nasopharyngeal cancer may be a genetic disease. Recently, the correlation between certain genetic factors that determine HLA and nasopharyngeal carcinoma has been found. There are reports of chromosomal aberrations in peripheral blood lymphocytes of families with high incidence of nasopharyngeal carcinoma and genetic susceptibility to nasopharyngeal cancer.
Clinical symptoms of nasopharyngeal carcinoma Early stage nasopharyngeal carcinoma can be asymptomatic because the tumor is small, located on the mucosal surface or accompanied by submucosal infiltration, and the tumor does not involve the opening of eustachian tube. The symptoms of early stage nasopharyngeal carcinoma include retractable blood stream most often, followed by hearing loss, tinnitus and occlusion in the ear.
Common clinical symptoms of primary cancer 1. Retractable bloody snot or rhinorrhea: Retractable bloody snot often occurs in the morning after waking up and humming out of the mouth with blood, and the amount of blood is not much, so it is often neglected by patients, or treated as hemoptysis to internal medicine or pulmonary medicine. Because of the brittle blood vessels in the nasopharyngeal cavity and the absence of mucous membrane covering the exterior of the tumor, it is easy to have the symptoms of bloody nasal discharge. Retractable blood is one of the early symptoms of nasopharyngeal cancer, which should be taken seriously by patients and physicians.
2.Tinnitus, hearing loss and occlusion in the ear: If nasopharyngeal cancer occurs in the lateral wall of nasopharynx, pharyngeal fossa or upper lip of the opening of pharyngeal drum, unilateral tinnitus or hearing loss may occur when the tumor compresses the pharyngeal drum, and secretory otitis media may also occur. Unilateral tinnitus or hearing loss and occlusion in the ear is one of the symptoms of early stage nasopharyngeal carcinoma.
3.Nasal congestion: nasopharyngeal cancer mainly occurs in the anterior wall of nasopharyngeal apex, and it is easy to invade the posterior part of nasal cavity. Nasal congestion accounts for 48.6% of the symptoms at the time of treatment.
4.Headache: Headache is often a one-sided migraine, located in the frontal, temporal or occipital area. Mild headaches do not require treatment, while heavy ones need to take painkillers or even inject painkillers. There are many reasons for headache, but brain nerve damage or skull base bone destruction is often one of the reasons for headache. In advanced nasopharyngeal carcinoma, headache may be caused by the stimulation reflex of the terminal nerve of the first branch of trigeminal nerve at the dura mater.
Cranial nerve damage 1. Facial numbness: It refers to the numbness of facial skin, and clinical examination shows that pain and tactile sensation are reduced or disappeared. Tumor invading cavernous sinus often causes damage to branch 1 or branch 2 of trigeminal nerve; tumor invading foramen ovale, pre-stem area and branch 3 of trigeminal nerve often causes numbness or abnormal sensation of skin in front of auricle, temporal area, cheek, lower lip and chin.
2. Diplopia: Because the tumor invades the abducens nerve, it often causes double shadow in outward vision. Invasion of talocrural nerve often causes inward strabismus and diplopia. It is often damaged together with trigeminal nerve.
3.Tongue muscle atrophy and tongue extension obliquity: nasopharyngeal cancer directly invades or lymph nodes metastasize to the posterior region of the caudate or the subglottic nerve canal, which invades the subglottic nerve and causes tongue extension obliquity to the diseased side, accompanied by tongue muscle atrophy on the diseased side. If the inferior lingual nerve is damaged bilaterally, it will cause difficulty in tongue extension. The incidence of tongue extension deviation is second only to facial palsy and diplopia.
4. Eyelid ptosis and eye fixation: it is related to the damage of the dynamic eye nerve. Visual loss or loss of vision is associated with optic nerve damage or orbital cone invasion.
5. Hoarseness and dysphagia: associated with damage to the vagus nerve and the glossopharyngeal nerve.
C. Swollen cervical lymph nodes The percentage of patients with nasopharyngeal cancer with swollen cervical lymph nodes as the first symptom is 36.5%, and the percentage of those with cervical lymph node metastasis at the time of treatment is 70.6%. Nasopharyngeal cancer is characterized by early metastasis of cervical lymph nodes and high metastasis rate. Metastatic lymph nodes are often multiple hard masses of different sizes, which generally increase in number from small to large as the disease progresses and gradually fuse into huge masses with restricted mobility. Usually metastasis is from the upper to lower neck, and about half of the patients have double neck metastasis, while metastasis to the preauricular lymph nodes is less common.
Distant metastasis The rate of distant metastasis of nasopharyngeal cancer is high, which is obviously related to whether the primary tumor invades outside the nasopharyngeal cavity, whether there is metastasis in cervical lymph nodes and the size and location. The rate of distant metastasis is higher if the tumor invades the oropharynx or nasal cavity. The site of metastasis can be single or multiple. The common sites of distant metastasis are bone, lung and liver. Bone metastasis is more common in the spine, pelvis and extremities. Metastases to the thorax, abdomen, mediastinal lymph nodes, inguinal lymph nodes, etc. can also occur, and metastases to the kidneys, adrenal glands and retroperitoneum can be detected early by CT.