Oral cancer is a disease with very poor prognosis because it is not recognised and treated when small and early.

INCIDENCE.

-Squamous cell (epidermoid) carcinoma comprises 90% of all oral malignant tumours and 5% of all human malignancies.

-The peak incidence in the UK and the USA is from 55 to 75 years of age, whereas in India it is from 40 to 45 years of age.

-Oral cancer is a very frequent malignancy in India, Sri Lanka and some Eastern countries, probably related to habits of betel-nut chewing and reversed smoking .

– There is a definite male preponderance.
-It can occur anywhere in the mouth but certain sites are more commonly involved.

-These sites, in descending
order of frequency, are: the lips (more commonly lower),
tongue, anterior floor of mouth, buccal mucosa in the region
of alveolar lingual sulcus, and palate.

ETIOLOGY.

As with other forms of cancer, the etiology of squamous cell carcinoma is unknown. But a number of etiological factors have been implicated:
Strong association:
i) Tobacco smoking and tobacco chewing causing leukoplakia is the most important factor .

ii) Chronic alcohol consumption.
iii) Human papilloma virus infection, particularly HPV 16, 18 and 33 types.

Weak association:
i) Chronic irritation from ill-fitting denture or jagged teeth.
ii) Submucosal fibrosis as seen in Indians consuming excess of chillies.
iii) Poor orodental hygiene.
iv) Nutritional deficiencies.
v) Exposure to sunlight (in relation to lip cancer).
vi) Exposure to radiation.
vii) Plummer-Vinson syndrome, characterised by atrophy
of the upper alimentary tract.

The most common molecular alterations in oncogenes
seen in squamous cell carcinoma of the oral cavity are in
p16, p53, cyclin D, p63, PTEN, and EGFR.

MORPHOLOGIC FEATURES.

Grossly, squamous cell carcinoma of oral cavity may have the following types

i) Ulcerative type—is the most frequent type and is
characterised by indurated ulcer and firm everted or
rolled edges.
ii) Papillary or verrucous type—is soft and wart-like growth.
iii) Nodular type—appears as a firm, slow growing submucosal nodule.
iv) Scirrhous type—is characterised by infiltration into
deeper structures.

*All these types may appear on a background of leukoplakia or erythroplasia of the oral mucosa.
Enlarged cervical lymph nodes may sometimes be present.

Histologically.

– squamous cell carcinoma ranges from well-differentiated keratinising carcinoma to highly undifferentiated neoplasm . -Changes of epithelial dysplasia are often present in the surrounding
areas of the lesion.

–Carcinoma of the lip and intraoral squamous carcinoma are usually always well-differentiated

source -textbook of pathology for dental students harsh mohan