2. Hairy leukoplakia Distinctive oral lesion Seen in immunocompromised patients 80% of patients with hairy leukoplakia have HIV infection

3. Hairy leukoplakia Takes the form of – White or black – Confluent – Patches of Fluffy (hairy) – Hyperkeratotic thickenings – Almost always on the lateral border of the tongue

4. Hairy Leukoplakia

5. Squamous Cell Carcinoma Oral Cavity

6. Squamous Cell Carcinoma 95% of cancers of Head and Neck are Squamous Cell Carcinomas arising most commonly in the oral cavity Head and Neck Squamous Cell Carcinoma - HNSCC HNSCC is the 6 th most common cancer in the world today Long term survival is 50%

7. Squamous Cell Carcinoma Long term survival is only 50% because – Oral cancer is diagnosed in advanced state – Frequent development of multiple primary tumours

8. Squamous Cell Carcinoma – Pathogenesis Multifactorial North America and Europe - – Middle aged men – Chronic abusers of smoked tobacco – Family history – HPV infection – Actinic radiation - Sunlight (lower lip)

9. Squamous Cell Carcinoma – Pathogenesis Multifactorial Outside of North America and Europe - – Chewing of betel quid - Paan in India – Betel quid contains » Areca nut, Slaked lime, Tobacco wrapped in betel leaf

10. Squamous Cell Carcinoma Molecular biology – Development of squamous cell carcinoma a multistep process involving a sequential activation of oncogenes and inactivation of tumour suppressor genes in a clonal population of cells.

11. Squamous Cell Carcinoma Molecular biology – Loss of chromosomal regions 3p and 9p21 - inactivation of p16 which is a suppressor of cyclin dependent kinase – Loss of chromosome 17p with mutation of p53 tumour suppressor gene – Deletions of 4q, 6p, 8p 11q, 13q, and 14q

12. Squamous Cell Carcinoma Morphology – May arise anywhere in the oral cavity Ventral surface of tongue, floor of mouth, lower lip, soft palate and gingiva – Preceded by premalignant lesions

13. Squamous Cell Carcinoma Morphology – Early stages Raised firm, pearly plaques Irregular roughened or verrucous thickening – Later Ulcerated, protruding masses Irregular, firm, and indurated (rolled) borders

14. Squamous Cell Carcinoma Morphology - Histology – Begin as dysplastic lesions – May or may not progress to full thickness dysplasia prior to invasion – Patterns range from Well differentiated keratinizing Anaplastic, Sarcomatoid – Degree of keratinization does not correlate with behaviour

15. Squamous Cell Carcinoma Morphology - Histology – Tend to infiltrate locally before metastasizing – Routes of extension depends on primary site – Favored sites of metastasis Cervical lymph nodes (local metastasis) Mediastinal lymph nodes (distant metastasis), lungs, liver and bones. (often occult)