L27 Mouth cancer: epidemiology and aetiology Flashcards
What are the most frequent sites of mouth cancer?
List some head and neck cancers.
- Skin
- Nose and sinuses
- Nasopharynx
- Oropharynx
- Oral cavity
- Pharynx
- Larynx
- Associated bone
What malignant diseases affect skin and mucosa?
Skin:
- SCC
- BCC
- Malignant melanoma
Mucosa:
- SCC
- Soft tissue sarcomas (fibrosarcoma, liposarcoma)
- Malignant lymphoma
Describe the epidemiology of mouth cancer.
- Relatively rare
- Twice as common in men
- 2386 deaths in the UK in 2014
- Predominantly a disease of the elderly but in recent years has become more common in younger people
What is the most common oral malignant neoplasm?
Squamous cell carcinoma (accounts for more than 90% of oral malignant neoplasms)
What is the 10 year survival rate for intra-oral SCC?
- 19-59%
- Poor prognosis
What is the average size of intraoral SCC ar presentation?
3-4cm (large)
Where is mouth cancer more common?
More common in India.
How does social class relate to mouth cancer?
- Oral cancer 3 times more common in social class V (most depriveed) than social class I
Name some aetiological factors for mouth cancer.
- Tobacco
- Alcohol
- UV light (lip cancer)
- Betel chewing
- Infection
- Irradiation
- Diet and nutrition
- Dental factors
- Immunosuppression
- Occupation
Explain how tobacco is a risk factor for mouth cancer.
- Over 90% of patients with oral cancer use tobacco in some form
- Pipes, cigars cigarettes
- Reverse smoking
- Oral tobacco products (snuff/snus) were banned in the UK in 1992
Explain how betel chewing is a risk factor for mouth cancer.
- Areca nut wrapped in betel leaf with added tobacco
- Users develop leukoplakia
- Can also develop submucous fibrosis (mottled, marbled, thick mucosa)
- Carcinoma develops in area of leukoplakia
Explain how alcohol is a risk factor for mouth cancer.
- 75-80% of pts frequently consume alcohol
- Dose/time relationship
- Drinking+smoking = highest risk
- Carcinogens found in distilled spirits (vodka, gin, rum, tequila, whiskey)
- Alcohol increases permeability of oral mucosa
What infections are risk factors for mouth cancer?
- Viral infection: Herpes simplex, HPV, EBV, HIV
- Candida
- Syphilis
Explain how HPV is a risk factor for mouth cancer.
- HPV related oropharyngeal cancer commonly affects tonsils, base of tongue and soft palate
- Associated with HPV-16 and -18
- Affects a younger age group
- Significant increase over the past decade
- Significantly better prognosis for HPV positive pts (up to 80% 5-year survival rate) than tonsillar cancer in non-HPV related cases
- More sensitive to chemo and radiotherapy than SCC
Explain how candida is a risk factor for mouth cancer.
- Clinical association between candidosis and oral cancer
- Iron deficiency is associated with oral candidosis
- Immunodeficiency is associated with oral candidosis
Chronic hyperplastic candidosis as a premalignant lesion:
- Leukoplakia so has premalignant potential
- Frequently clinically speckled (speckled leukoplakia are more often dysplastic or malignant than homogenous leukoplakia)
Explain how irradiation is a risk factor for mouth cancer.
- Strongly associated with cancer of the lower lip
- More common in men than women
- More common in people with outdoor occupations
- Rare in races with darker skin
- May be preceded by solar keratosis (actinic keratosis)
Explain how diet and nutrition are risk factors for mouth cancer.
- Emerging area of interest
- Dietary deficiencies, particularly of vitamin A (and related carotenoids), vit C, vit E, iron, selenium, folate and other trace elements have been linked to increased risk of mouth cancer
- Many studies have found that oral cancer patients have a history of low fruit and vegetable intake
- Intervention studies where diets have been supplemented have some shown some beneficial effect on pre-malignant conditions and reducing the risk of a second oral cancer but further research is necessary
Explain how dental factors may act as risk factors for mouth cancer.
- Poor oral hygiene, sharp teeth, sharp restorations, ill fitting dentures have all been implicated in the aetiology of oral cancer
- Many patients with oral cancer have poor dentitions
- Difficult to determine a causal relationship, lots of confounding factors
- Little real evidence for a causative association
- However, mechanical irritation can act as a promotor in experimental carcinogenesis
Explain how immunosuppresion can act as a risk factor for mouth cancer.
- Increased incidence of mouth cancer in renal transplant patients
- Possible increased incidence in those with HIV infection
- Smoking, alcohol and iron deficiency suppress cell mediated immunity
Explain the pathology of oral squamous cell carcinoma.
- SCC is a malignant neoplasm derived from the stratified squamous epithelium of the oral mucosa
- Histologically the tissues are well differentiated (obviously squmaous epithelium)
- As SCC progresses, it invades the lamina propria, underlying tissues, muscles, salivary glands and bone
Describe how oral SCC spreads.
- Cancer invades nerves and spreads down the sheath
- Invades the bone of the mandible and fills marrow spaces
- Spreads through lymphatics and reaches nodes of neck
Aka perineural invasion, lymphatic permeation and vascular invasion
Blood borne metastases (to lung, liver, bone etc) tends to be a late phenomenon.
Describe the histological pressentation of oral SCC.
- Islands, strands and branching trabeculae of squamous cells
- Budded architecture
- Usually well-defined basal layer, bulk consists of prickle cells; often central keratinisation
- Cells are clearly cytologically malignant: cellular and nuclear pleomorphism, increased mitoses, abnormal mitoses
- Variable inflammatory reaction in surrounding fibrous stroma
- Keratin present
What are the 2 ways that oral SCC advances?
- Cohesive: cancer invades on broad front (better prognosis)
- Non-cohesive: separate islands of tumour extending along the advancing edge, poorer prognosis
How is oral SCC managed?
- Surgical excision
- Non-surgical:
- Radiotherapy +/- chemotherapy
- Primary management following surgical excision, except for oropharyngeal which is primary radio/chemotherapy initially and then potentially surgery
What is the 5 year survival rate for oral SCC?
56%
What factors affect prognosis following oral SCC diagnosis?
- Site (lip has best prognosis)
- Size
- Degree of differentiation
- Lymph node metastasis (poorer prognosis if lymph node involvement already present at initial appointment)
- Age of patient, co-morbidities, general level of fitness
Is there a better prognosis for well differentiated or poorly differentiated oral SCC?
Well differentiated (grade I) = better 5 year survival rate
What factors influence risk of metastasis?
Size, site and thickness of tumour dictates risk of metastasis.
Deeper penetration (thickness) of tumour = higher risk of metastasis and poorer survival.
How is oral SCC staged?
TNM system
T = tumour size
N = lymph nodes
M = metastasis
