The pharynx or throat is a tube-like structure that starts behind the nasal cavity and ends its course into the larynx or voice box. The esophageal track starts after the pathway of bolus or food chewed from the pharynx, or the throat region passes into the esophagus by peristaltic movements. After which, it enters the stomach. The passage of air is also through the pharynx to the lungs. A thin tissue or flap called the epiglottis over the larynx prevents the passage of food into the larynx and the lungs. The nasopharyngeal cells line the mucosa of the nasopharynx layer.
How Is Pharynx Divided Based on the Location?
The pharynx is divided into three parts based on the location:
The part of the pharynx behind the nasal cavity is the nasopharynx.
The oropharynx is below the nasopharynx.
The hypopharynx lies behind the voice box or larynx.
What Is Nasopharyngeal Carcinoma or NPC?
Cancers of the nasopharynx spread via the lymphatic route into the neck or behind the ears. The World Health Organization defines NPC or Nasopharyngeal carcinoma as carcinoma or cancer arising in the nasopharyngeal mucosa that exhibits ultrastructural evidence of squamous cell differentiation or in the light microscopic examination exhibits the same squamous differentiation.
This carcinoma is mainly classified based on the differentiation aspect into three types. Most NPC is exophytic (almost around 75% of the tumors), encompassing both non-keratinizing carcinoma and squamous cell carcinomas.
What Is the Etiology of Nasopharyngeal Carcinoma?
The etiology of this tumor is linked to a multi-factorial cause though environmental carcinogens are researched to be the most common risk factor for developing NPC. Though in maxillofacial surgery literature, the reports of NPC are comparatively rare amongst the white population ethnically. They are common, especially amongst South East Asian countries like China, Indonesia, Vietnam, and Africa.
What Are the Risk Factors of Nasopharyngeal Carcinoma?
Nasopharyngeal carcinoma occurs mostly in the fourth to sixth decade of life with a 3:1 ratio prevalence in males to females.
Research indicates environmental carcinogens like Nitrosamines to be the most causative risk factor for developing NPC in an individual with no medical or family history of oncogenicity. Similarly, frequent radiation exposure due to radiation therapy and formaldehyde exposure also have been implicated as causes.
Chronic smokers are at a definitive or increased risk for nasopharyngeal cancers because of the carcinogenic impact of unburned tobacco or cigarette smoking.
Even though this disease is multi-factorial or multi-causative, primary evidence is that in most of the reported cases of NPC, the individual suffers from an EBV (Epstein-Barr virus) infection. It is indicative that the EBV virus may have a potential oncogenic role in increasing viral titers and breaching the immune system defense making the person prone to NPC.
What Are the Types of Nasopharyngeal Carcinoma?
Under light microscopy, the pathologic examination of NPCA tissue can be either well-differentiated (that look like normal tissues), poorly differentiated (that don’t resemble normal physiologic tissue), or undifferentiated (that totally vary in appearance from the standard physiologic tissue structure).
Based on these characteristics under microscopy, there are mainly three types of Nasopharyngeal carcinoma.
Non-keratinizing form of NPC or Lymphoepithelioma.
Keratinizing squamous cell carcinoma.
Basaloid squamous cell carcinoma.
What Is the Histopathology of Nasopharyngeal Carcinoma?
Keratin is strongly immunoreactive and helps confirm the diagnosis of carcinoma. Hence, the non-keratinizing form of NPC is undifferentiated and histopathologically revealed to be of solid sheets of large tumor or cancer cells arranged irregularly in the form of island pattern or as trabeculae intermingled with inflammatory cell elements. The germinal centers are reactive and are without a well-defined border or mantle.
Also, the cell nuclei are usually prominent in healthy physiology. Still, in NPC, the appearance of the nucleoli is altered with the nucleus being vesicular, the nuclear chromatin being either transparent or vesicular, and with a high nucleoplasm to cytoplasm ratio. Profound nuclear pleomorphism (variability in size, shape, and staining of the nuclei) and syncytial cell nests separated by lymphoid cells are well observable to study the epithelial nature of this tumor via keratin immunohistochemistry.
What Is the Differential Diagnosis of Nasopharyngeal Carcinoma?
What Are the Clinical Features of Nasopharyngeal Carcinoma?
The early stages of NPC are usually very asymptomatic. Patients suffering from NPC typically present with asymptomatic cervical mass at the level of the jugular lymph nodes of the neck or the posterior cervical triangle in the neck. Blood-tinged saliva or bloody discharges from the nose accompanied by nasal congestion is a common clinical feature. Headaches, sore throat, or hearing loss are other symptoms exhibited by the patient alongside the main clinical features.
How Is Nasopharyngeal Carcinoma Diagnosed?
The physician usually recommends gross specimen biopsy obtained from the nasopharynx region of the patient, either randomized or from the posterior, lateral, or superior wall of the nasopharynx (the fossa of Rosenmüller in the lateral wall being the most common site of development). The endoscopic evaluation also helps detect this tumor, and mainly immunohistochemistry and immunoreactivity tests confirm the diagnosis.
How Is Nasopharyngeal Carcinoma Treated?
As NPC is highly cancerous or malignant in most cases with a very high-grade incidence of spread either by lymphatics or hematogenous route, irradiation of the tumor along with surgical resection is the mainline treatment of choice. However, for the disseminated forms of NPC, chemotherapy follows surgical resection of the tumor. At the advanced stage (T3/T4) of the tumors, craniofacial linkage (reported in many cases as NPC) can cause the spread of the tumor to the paranasal sinuses, orbit, or directly extend into the base of the skull. Metastasis of this cancer offers a very poor prognosis even after treatment.
To conclude, nasopharyngeal carcinoma is very invasive due to its tendency to invade surrounding tissues. Hence early detection of this asymptomatic malignancy remains the key to prevention and surgeon’s timely management (irradiation & surgical resection of tumor) after confirmatory diagnosis by biopsy, immunohistochemistry, and endoscopy can improve long-term survival rates in these cancer patients. If one experiences any of the above-mentioned clinical features, then one must seek medical help as early as possible.
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